media: v4l2: Extend pixel formats to unify single/multi-planar handling (and more)

This is part of the multiplanar and singleplanar unification process.
v4l2_ext_pix_format is supposed to work for both cases.

We also add the concept of modifiers already employed in DRM to expose
HW-specific formats (like tiled or compressed formats) and allow
exchanging this information with the DRM subsystem in a consistent way.

Note that only V4L2_BUF_TYPE_VIDEO_[OUTPUT,CAPTURE] are accepted in
v4l2_ext_format, other types will be rejected if you use the
{G,S,TRY}_EXT_PIX_FMT ioctls.

New hooks have been added to v4l2_ioctl_ops to support those new ioctls
in drivers, but, in the meantime, the core takes care of converting
{S,G,TRY}_EXT_PIX_FMT requests into {S,G,TRY}_FMT so that old drivers can
still work if the userspace app/lib uses the new ioctls.

The conversion is also done the other around to allow userspace
apps/libs using {S,G,TRY}_FMT to work with drivers implementing the
_ext_ hooks.

Signed-off-by: Boris Brezillon <boris.brezillon@collabora.com>
Signed-off-by: Helen Koike <helen.koike@collabora.com>
---

Changes in v6:
 The main change here was fixing the conversion, so planes reflects color planes,
 and to implement this properly I made major refactors compared to the previous
 version.
- struct v4l2_plane_ext_pix_format removed, using struct v4l2_plane_pix_format instead (Tomasz)
- refer to drm_fourcc.h in struct v4l2_ext_pix_format docs (Hans)
- reorder colorimetry fields in struct v4l2_ext_pix_format (Hans)
- do not set Ext ioctls as valid for vid_out_overlay (Tomasz)
- refactor conversion functions, so planes are color planes (Tomasz)
- Don't explicitly check for e->modifier != 0 in v4l2_ext_pix_format_to_format() (Tomasz)
- Use "ef" for extended formats in the framework for consistency (Tomasz)
- Handle xfer_func field in conversions (Tomasz)
- Zero reserved fields in v4l_s_ext_pix_fmt() and v4l_try_ext_pix_fmt() (Tomasz)
- Refactor format functions to use v4l_fmt_ioctl_via_ext()
- Several fixes/refactoring/changes
- Remove EXT API for touch devices

Changes in v5:
- change sizes and reorder fields to avoid holes in the struct and make
  it the same for 32 and 64 bits
- removed __attribute__ ((packed)) from uapi structs
- Fix doc warning from make htmldocs
- Updated commit message with EXT_PIX prefix for the ioctls.

Changes in v4:
- Use v4l2_ext_pix_format directly in the ioctl, drop v4l2_ext_format,
making V4L2_BUF_TYPE_VIDEO_[OUTPUT,CAPTURE] the only valid types.
- Add reserved fields
- Removed num_planes from struct v4l2_ext_pix_format
- Removed flag field from struct v4l2_ext_pix_format, since the only
  defined value is V4L2_PIX_FMT_FLAG_PREMUL_ALPHA only used by vsp1,
  where we can use modifiers, or add it back later through the reserved
  bits.
- In v4l2_ext_format_to_format(), check if modifier is != MOD_LINEAR &&
  != MOD_INVALID
- Fix type assignment in v4l_g_fmt_ext_pix()
- Rebased on top of media/master (post 5.8-rc1)

Changes in v3:
- Rebased on top of media/master (post 5.4-rc1)

Changes in v2:
- Move the modifier in v4l2_ext_format (was formerly placed in
  v4l2_ext_plane)
- Fix a few bugs in the converters and add a strict parameter to
  allow conversion of uninitialized/mis-initialized objects