drm/i915/selftest_migrate: Check CCS meta data clear

Extend the live migrate selftest, to verify the ccs surface clearing
during the Flat-CCS capable lmem obj clear.

v2:
  Look at right places for ccs data [Thomas]

Signed-off-by: Ramalingam C <ramalingam.c@intel.com>
Reviewed-by: Thomas Hellstrom <thomas.hellstrom@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220405150840.29351-8-ramalingam.c@intel.com