[media] dib8000: fix a warning

drivers/media/dvb-frontends/dib8000.c: In function 'dib8000_wait_lock':
drivers/media/dvb-frontends/dib8000.c:3972:1: warning: 'value' may be used uninitialized in this function [-Wmaybe-uninitialized]
drivers/media/dvb-frontends/dib8000.c:2419:6: note: 'value' was declared here

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