tests: Add kms_mmap_write_crc for cache coherency tests

This program can be used to detect when the writes don't land in scanout due
cache incoherency. Although this seems a problem inherently of non-LCC machines
("Atom"), this particular test catches a cache dirt on scanout on LLC machines
as well. It's inspired in Ville's kms_pwrite_crc.c and can be used also to test
the correctness of the driver's begin_cpu_access (TODO end_cpu_access).

To see the need for flush, one has to run this same binary a few times cause
it's not 100% reproducible (in my Core machine it's always possible to catch
the problem by running it at most 5 times).

Signed-off-by: Tiago Vignatti <tiago.vignatti@intel.com>

tests/Makefile.sources

@@ -163,6 +163,7 @@ TESTS_progs = \
 	kms_3d \
 	kms_fence_pin_leak \
 	kms_force_connector \
+	kms_mmap_write_crc \
 	kms_pwrite_crc \
 	kms_sink_crc_basic \
 	prime_udl \