[media] staging: lirc_sir: remove dead code

lirc_sir uses the CONFIG_SA1100_BITSY Kconfig macro. But its Kconfig
symbol was removed in v2.4.13. So remove dead code associated with it.

Signed-off-by: Paul Bolle <pebolle@tiscali.nl>
Signed-off-by: Alexander Shiyan <shc_work@mail.ru>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>