[media] ir-rx51: Trivial fixes

-Fix typo
-Change pwm_timer_num type to match type in platform data
-Remove extra parenthesis
-Replace magic constant with proper bit defintions
-Remove duplicate exit pointer

Signed-off-by: Timo Kokkonen <timo.t.kokkonen@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>