kms_fbc_crc: Add a CRC based FBC test

kms_fbc_crc: Add a CRC based FBC test

kms_fbc_crc will perform various write operations to the scanout buffer
whilc FBC is enabled. CRC checks will be used to make sure the
modifcations to scanout buffer are detected.

The operations include:
 - page flip
 - GTT mmap
 - CPU mmap
 - blit
 - rendercopy
 - context switch + rendercopy
 - combination of a page flip and each operation listed above

v2: Use gem_sw_finish instead of drmModeDirtyFB after CPU access
v3: Drop pwrite tests, call gem_bo_busy() after rendering, drop
    set_domain() calls after mmap access, wait for 2 vblanks

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>