[media] V4L: ov9740: Cleanup hex casing inconsistencies

Made all hex number casing use lower-case throughout the entire driver
for consistency.

Signed-off-by: Andrew Chew <achew@nvidia.com>
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>