media: i2c: ov5670: Use dev_err_probe in probe function

Replace the unusual const char *err_msg usage with dev_err_probe which
also handles -EPROBE_DEFER better by not printing the message to kmsg.

Signed-off-by: Luca Weiss <luca@z3ntu.xyz>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>