[media] media: s5p-mfc: fix broken pointer cast on 64bit arch

Unsigned int cannot be used to store casted pointer on 64bit
architecture, so correct such casts to properly use unsigned long
variables.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Signed-off-by: Kamil Debski <k.debski@samsung.com>
[k.debski@samsung.com: removed volatile and __iomem from cast]

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