drm/i915/selftests: Include <linux/prandom.h> instead of <linux/random.h>

drm/i915/selftests: Include <linux/prandom.h> instead of <linux/random.h>

Substitute the inclusion of <linux/random.h> header with
<linux/prandom.h> to allow the removal of legacy inclusion
of <linux/prandom.h> from <linux/random.h>.

Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Cc: Tvrtko Ursulin <tursulin@ursulin.net>
Cc: David Airlie <airlied@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>