media: cx23885-alsa: number of pages should be unsigned long

As reported by smatch:

	drivers/media//pci/cx23885/cx23885-alsa.c:83 cx23885_alsa_dma_init() warn: should 'nr_pages << 12' be a 64 bit type?

the number of patches should be unsigned long.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>