[media] rc: fix ghost keypresses with certain hw

With hardware that has to use ir_raw_event_store_edge to collect IR
sample durations, we were not doing an event reset unless
IR_MAX_DURATION had passed. That's around 4 seconds. So if someone
presses up, then down, with less than 4 seconds in between, they'd get
the initial up, then up and down upon pressing down.

To fix this, I've lowered the "send a reset event" logic's threshold to
the input device's REP_DELAY (defaults to 500ms), and with an
saa7134-based GPIO-driven IR receiver in a Hauppauge HVR-1150, I get
*much* better behavior out of the remote now. Special thanks to Devin
for providing the hardware to investigate this issue.

CC: stable@kernel.org
CC: Devin Heitmueller <dheitmueller@kernellabs.com>
Signed-off-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>