[media] saa7134: fix page size on some archs

On some archs, like tile, the PAGE_SIZE is not 4K. In the case
of tile arch, it can be either 16KB or 64KB.

Due to that, a warning is produced:
	drivers/media/pci/saa7134/saa7134.h:678:43: warning: large integer implicitly truncated to unsigned type [-Woverflow]

This is actually an error, as it will write trach to the DMA size
registers. The logic at saa7134-ts already does the right thing:

	saa_writeb(SAA7134_TS_DMA0, ((dev->ts.nr_packets-1)&0xff));
	saa_writeb(SAA7134_TS_DMA1, (((dev->ts.nr_packets-1)>>8)&0xff));
	/* TSNOPIT=0, TSCOLAP=0 */
	saa_writeb(SAA7134_TS_DMA2,
		((((dev->ts.nr_packets-1)>>16)&0x3f) | 0x00));

So, fix the driver to take larger page sizes into account.

Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>