V4L/DVB (6306): Few clenups for saa7134 resume code

*Disable DMA explictly on suspend
*Enable DMA on resume, after all buffers were configured
*Disable overlay on resume - apps should enable it when X is resumed

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