media: imx274: don't hard-code the subdev name to DRIVER_NAME

Forcibly setting the subdev name to DRIVER_NAME (i.e. "IMX274") makes
it non-unique and less informative.

Let the driver use the default name from i2c, e.g. "IMX274 2-001a".

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>