media: v4l: mt9v032: Disable clock on error paths

mt9v032_power_on() leaves clk enabled in case of errors,
but it is not expected by its callers.
There is a similar problem in mt9v032_registered().

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>