media: rc: fix timeout handling after switch to microsecond durations

Commit 528222d8 ("media: rc: harmonize infrared durations to
microseconds") missed to switch some timeout calculations from
nanoseconds to microseconds. This resulted in spurious key_up+key_down
events at the last scancode if the rc device uses a long timeout
(eg 100ms on nuvoton-cir) as the device timeout wasn't properly
accounted for in the keyup timeout calculation.

Fix this by applying the proper conversion functions.

Cc: stable@vger.kernel.org
Fixes: 528222d8 ("media: rc: harmonize infrared durations to microseconds")
Signed-off-by: Matthias Reichl <hias@horus.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>