media: lirc: remove LIRCCODE and LIRC_GET_LENGTH

LIRCCODE is a lirc mode where a driver produces driver-dependent
codes for receive and transmit. No driver uses this any more. The
LIRC_GET_LENGTH ioctl was used for this mode only.

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