media: rc/ir-rx51: Drop empty platform remove function

A remove callback just returning 0 is equivalent to no remove callback
at all. So drop the useless function.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>