Calculate lirc features when necessary, and add LIRC_{S,G}ET_REC_MODE
cases to ir_lirc_ioctl.

This makes lirc_dev_fop_ioctl() unnecessary since all cases are
already handled by ir_lirc_ioctl().
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>