V4L/DVB (12199): remove redundant tests on unsigned

input, inp and i are unsigned. When negative they are wrapped and caught by the
other test.

Cc: Andy Walls <awalls@radix.net>
Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Signed-off-by: Douglas Schilling Landgraf <dougsland@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>