[media] gspca_pac7302: increase default value for white balance temperature

The current white balance temperature default value is 4, which is much too small (possible values are 0-255).
Improve the picture quality by increasing the default value to 55, which is the default value used by the Windows driver.

Signed-off-by: Frank Schäfer <fschaefer.oss@googlemail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>