tests/kms_fb_crc: fix the reference CRC checking
tests/kms_fb_crc: fix the reference CRC checking

Now we get the reference CRCs on separate untiled FBs just to make
sure FBC is not there to mess the CRC computation. We also get the
reference CRCs for buffers that were drawn in the same way that we
draw them during the tests, so we can finally get rid of that FIXME
comment we have!

With this, kms_fbc_crc now actually tests something instead of just
wasting CPU cycles...

Fixes regression introduced by:

commit 562bbe12f6fb75811a746c742a28d32a17b26aa9
Author: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>
Date:   Fri Feb 27 22:04:18 2015 +0100
    tests: Remove usage of igt_crc_equal and _non_null

Cc: Daniel Vetter <c1b6782c4af8f0673da8923a0702a1832e5940f4@ffwll.ch>
Signed-off-by: Paulo Zanoni <cc0e04a2103c45cd195651d976f79813d0f66bdf@intel.com>

dlespiau/checkmate-test-igt,tiagovignatti/intel-gpu-tools,chenxianqin/intel-gpu-tools,mv0/intel-gpu-tools,tiagovignatti/intel-gpu-tools,tiagovignatti/intel-gpu-tools,mv0/intel-gpu-tools,chenxianqin/intel-gpu-tools,mv0/intel-gpu-tools,mv0/intel-gpu-tools,tiagovignatti/intel-gpu-tools,chenxianqin/intel-gpu-tools,dlespiau/checkmate-test-igt,dlespiau/checkmate-test-igt,chenxianqin/intel-gpu-tools,dlespiau/checkmate-test-igt