A few fixes for 4.18:
- fix a read past the end of an array due to vega20 changes
- fix driver on systems with non-4K pages
- fix locking with pageflipping in DC that could lead to a sleep while atomic
- fix VCN firmware version reporting for upcoming firmware

Signed-off-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180628032641.2765-1-alexander.deucher@amd.com