media: imx274: remove binning enum

Binning enum is unused. Remove from driver.

Suggested-by: Sakari Ailus <sakari.ailus@ifi.fi>
Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>
Reviewed-by: Luca Ceresoli <luca@lucaceresoli.net>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>