media: rc-core: consistent use of rc_repeat()

The NEC decoder and the Sanyo decoders check if dev->keypressed is true
before calling rc_repeat (without holding dev->keylock).

Meanwhile, the XMP and JVC decoders do no such checks.

This patch makes sure all users of rc_repeat() do so consistently by
removing extra checks in NEC/Sanyo and modifying the check a bit in
rc_repeat() so that no input event is generated if the key isn't pressed.

Signed-off-by: David Härdeman <david@hardeman.nu>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>