media: secocec: fix ir address shift

The actual value of the RC5 System Number (address) is stored in the
IR_READ_DATA common register masked with 0x1F00 so it have to be shifted
by 8 bits.

Signed-off-by: Ettore Chimenti <ek5.chimenti@gmail.com>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>