media: i2c: ov2740: get OTP data ready before nvmem registration

The OTP data was not ready after registered as nvmem device, it is
risky as the nvmem read may happen once the device exists, this patch
get the OTP data ready before registering the nvmem device. OTP data
missing should not break the normal camera sensor probe, so use a
warning instead of an error message.

Signed-off-by: Bingbu Cao <bingbu.cao@intel.com>
Signed-off-by: Qingwu Zhang <qingwu.zhang@intel.com>
Suggested-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>