media: dvb-frontends/drxk: initialize err to 0

Fix a compiler warning:

drivers/media/dvb-frontends/drxk_hard.c: In function 'drxk_read_ucblocks':
drivers/media/dvb-frontends/drxk_hard.c:6673:21: warning: 'err' may be used uninitialized [-Wmaybe-uninitialized]
 6673 |         *ucblocks = (u32) err;
      |                     ^~~~~~~~~
drivers/media/dvb-frontends/drxk_hard.c:6663:13: note: 'err' was declared here
 6663 |         u16 err;
      |             ^~~

Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>