media: i2c: ov9640: add missing SPDX identifiers

Add missing SPDX identifiers to .c and .h files of the sensor driver.

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>