drm/i915/selftests: Add tiled blits selftest

Extend coverage of the blitter client by exercising conversion to and
from tiled sources. In the process we perform spot checks to verify that
the tiling/detiling is being applied correctly, along with position
invariance of the tiling parameters.

Signed-off-by: Zbigniew Kempczyński <[email protected]>
Cc: Chris Wilson <[email protected]>
Cc: Joonas Lahtinen <[email protected]>
Reviewed-by: Chris Wilson <[email protected]>
Signed-off-by: Chris Wilson <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]

Author: wegorz76