media: i2c: ov2740: Small cleanups

Small cleanups for the driver, namely removal of OV2740_NUM_SUPPLIES
macro, use of unsigned int for a loop and printing the missing "0x" for a
hexadecimal number.

Co-developed-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Hans Verkuil <hverkuil@xs4all.nl>