media: i2c: ov9640: make array of supported formats constant

An array which defines sensor's supported formats is not written anywhere,
so it can be constant.

Signed-off-by: Petr Cvek <petrcvekcz@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>