V4L/DVB (8396): video: Fix Kbuild dependency for VIDEO_IR_I2C

Instead of letting VIDEO_IR_I2C to be selected by VIDEO_IR, if I2C, convert it
into a symbol that depends on both VIDEO_IR and I2C.

Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>