media: i2c: ov9282: Add missing clk_disable_unprepare to error path

If ov9282_power_on failed the I2C write, it returned without releasing
clocks or regulators. Fix this.

Fixes: 6f7def3d ("media: i2c: ov9282: Add selection for CSI2 clock mode")
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>