[media] v4l/dvb: fix compiler warnings

[media] v4l/dvb: fix compiler warnings

media_build/v4l/stb6100.c: In function 'stb6100_read_reg':
media_build/v4l/stb6100.c:161:6: warning: variable 'rc' set but not used [-Wunused-but-set-variable]
media_build/v4l/cx24110.c: In function 'cx24110_read_ucblocks':
media_build/v4l/cx24110.c:515:6: warning: variable 'lastbyer' set but not used [-Wunused-but-set-variable]
media_build/v4l/dib9000.c: In function 'dib9000_mbx_process':
media_build/v4l/dib9000.c:711:6: warning: variable 'tmp' set but not used [-Wunused-but-set-variable]
media_build/v4l/zl10353.c: In function 'zl10353_init':
media_build/v4l/zl10353.c:562:6: warning: variable 'rc' set but not used [-Wunused-but-set-variable]
media_build/v4l/stv0297.c: In function 'stv0297_set_frontend':
media_build/v4l/stv0297.c:417:16: warning: variable 'starttime' set but not used [-Wunused-but-set-variable]
media_build/v4l/lgs8gxx.c: In function 'lgs8gxx_set_mode_manual':
media_build/v4l/lgs8gxx.c:265:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
media_build/v4l/af9013.c: In function 'af9013_statistics_work':
media_build/v4l/af9013.c:517:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
media_build/v4l/stv090x.c: In function 'stv090x_optimize_track':
media_build/v4l/stv090x.c:2845:23: warning: variable 'rolloff' set but not used [-Wunused-but-set-variable]
media_build/v4l/stv090x.c: In function 'stv090x_algo':
media_build/v4l/stv090x.c:3177:28: warning: variable 'no_signal' set but not used [-Wunused-but-set-variable]
media_build/v4l/it913x-fe.c: In function 'it913x_fe_read_ber':
media_build/v4l/it913x-fe.c:636:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
media_build/v4l/it913x-fe.c: In function 'it913x_fe_get_frontend':
media_build/v4l/it913x-fe.c:661:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
media_build/v4l/it913x-fe.c: In function 'it913x_fe_set_frontend':
media_build/v4l/it913x-fe.c:694:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
media_build/v4l/m88rs2000.c: In function 'm88rs2000_set_fec':
media_build/v4l/m88rs2000.c:657:6: warning: variable 'ret' set but not used [-Wunused-but-set-variable]
media_build/v4l/dst_ca.c: In function 'ca_send_message':
media_build/v4l/dst_ca.c:480:15: warning: variable 'ca_message_header_len' set but not used [-Wunused-but-set-variable]
media_build/v4l/smssdio.c: In function 'smssdio_interrupt':
media_build/v4l/smssdio.c:117:11: warning: variable 'isr' set but not used [-Wunused-but-set-variable]

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>