[media] lgdt330x: fix behavior of read errors in lgdt330x_read_ucblocks

initialize *ucblocks to zero & fix the following build warning:

lgdt330x.c: In function "lgdt330x_read_ucblocks":
lgdt330x.c:288:6: warning: variable "err" set but not used
[-Wunused-but-set-variable]

Signed-off-by: Michael Krufky <mkrufky@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>