[media] xc4000: Fix a few warnings

drivers/media/tuners/xc4000.c: In function ‘check_firmware’:
drivers/media/tuners/xc4000.c:1048:45: warning: ‘fw_minor’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/media/tuners/xc4000.c:1048:39: warning: ‘fw_major’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/media/tuners/xc4000.c:1062:39: warning: ‘hw_minor’ may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/media/tuners/xc4000.c:1062:33: warning: ‘hw_major’ may be used uninitialized in this function [-Wmaybe-uninitialized]

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>