[media] fimc-lite: Fix the variable type to avoid possible crash

Changing the variable type to 'int' from 'unsigned int'. Driver
logic expects the variable type to be 'int'.

Signed-off-by: Shaik Ameer Basha <shaik.ameer@samsung.com>
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>