media: ts2020: Variable "utmp" in function ts2020_set_tuner_rf() could be uninitialized

In function ts2020_set_tuner_rf(), local variable "utmp" could
be uninitialized if function regmap_read() returns -EINVAL.
However, this value is used in if statement and written to
the register, which is potentially unsafe.

Signed-off-by: Yizhuo <yzhai003@ucr.edu>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>