media: rc: nec decoder should not send both repeat and keycode

When receiving an nec repeat, rc_repeat() is called and then rc_keydown()
with the last decoded scancode. That last call is redundant.

Fixes: 265a2988 ("media: rc-core: consistent use of rc_repeat()")

Cc: <stable@vger.kernel.org> # v4.14
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>