tests/kms_async_flips: Test all modifiers

Run the basic async flip test for all modifiers reported
by the plane (for the XRGB8888 format). The driver may not
support async flip with all modifiers so we allow this to fail.

v2: print output name along with the modifier

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Arun R Murthy <arun.r.murthy@intel.com>
Reviewed-by: Karthik B S <karthik.b.s@intel.com>