V4L/DVB (4026): Bttv-gpio-irq is no longer used, remove it

This functionality was used when remote control input for BTTV was handled
by a standalone module, to hook some functions of that module into the main 
bttv core.
Since that module is now extinct, this can go away

Signed-off-by: Ricardo Cerqueira <rmcc@linuxtv.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>