drm/vmwgfx: Implement virtual crc generation

crc checksums are used to validate the output. Normally they're part
of the actual display hardware but on virtual stack there's nothing
to automatically generate them.

Implement crc generation for the vmwgfx stack. This works only on
screen targets, where it's possibly to easily make sure that the
guest side contents of the surface matches the host sides output.

Just like the vblank support, crc generation can only be enabled via:
guestinfo.vmwgfx.vkms_enable = "TRUE"
option in the vmx file.

Makes IGT's kms_pipe_crc_basic pass and allows a huge number of other
IGT tests which require CRC generation of the output to actually run
on vmwgfx. Makes it possible to actually validate a lof of the kms and
drm functionality with vmwgfx.

Signed-off-by: Zack Rusin <zack.rusin@broadcom.com>
Acked-by: Martin Krastev <martin.krastev@broadcom.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240412025511.78553-3-zack.rusin@broadcom.com