drm/i915/selftests: Pick correct caching mode.

drm/i915/selftests: Pick correct caching mode.

Caching mode is HW dependent so pick a correct one using
intel_gt_coherent_map_type().

Cc: Andi Shyti <[email protected]>
Cc: Janusz Krzysztofik <[email protected]>
Cc: Jonathan Cavitt <[email protected]>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/10249
Signed-off-by: Nirmoy Das <[email protected]>
Acked-by: Jonathan Cavitt <[email protected]>
Reviewed-by: Andi Shyti <[email protected]>
Signed-off-by: Andi Shyti <[email protected]>
Link: https://patchwork.freedesktop.org/patch/msgid/[email protected]