media: rc: decoders do not need to check for transitions

Drivers should never produce consecutive pulse or space raw events. Should
that occur, we would have bigger problems than this code is trying to
guard against.

Note that we already log an error should a driver misbehave.

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