Virtual address space put the userspace in charge of their GPU
address space. It's up to userspace to bind bo into the virtual
address space. Command stream can them be executed using the
IB_VM chunck.

This patch add support for this configuration. It doesn't remove
the 64K ib size limit thought this limit can be extanded up to
1M for IB_VM chunk.

v2: fix rendering
v3: fix rendering when using index buffer
v4: make vm conditional on kernel support add basic va management
v5: catch the case when we already have va for a bo
v6: agd5f: update on top of ioctl changes
v7: agd5f: further ioctl updates
v8: indentation cleanup + fix non cayman
v9: rebase against lastest mesa + improvement from Marek & Michel
v10: fix cut/paste bug
v11: don't rely on updated radeon_drm.h

Signed-off-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>