V4L/DVB (6269): V4L: Fix a "scheduling while atomic" bug in saa7134

set_tvnorm can sleep in saa7134_i2c_xfer
(it will be called through tuner code)
but code calls it under spinlock. Fix that

Signed-off-by: Maxim Levitsky <maximlevitsky@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>