[media] em28xx: Fix a few warnings due to HVR-930C addition

drivers/media/video/em28xx/em28xx-cards.c:339:30: warning: ‘hauppauge_930c_gpio’ defined but not used [-Wunused-variable]
drivers/media/video/em28xx/em28xx-dvb.c: In function ‘em28xx_dvb_init’:
drivers/media/video/em28xx/em28xx-dvb.c:886:3: warning: ISO C90 forbids mixed declarations and code [-Wdeclaration-after-statement]

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