test: use valarray for raw image comparison
test: use valarray for raw image comparison

std::valarray can fuse elementwise operations across arrays for
more efficient comparison.

Signed-off-by: Scott D Phillips <869de412a74df48368498a2fabd4c27e6a0922a9@intel.com>
Reviewed-by: U. Artie Eoff <32aece0d55055227b44d04b7d0051cf3d04ee871@intel.com>
(cherry picked from commit 852cea1cdfc83e0b6531dfefda14badafc9ee206)

01org/iotg-lin-gfx-va-driver,01org/iotg-lin-gfx-va-driver,01org/iotg-lin-gfx-va-driver,01org/iotg-lin-gfx-va-driver,01org/iotg-lin-gfx-va-driver