[media] media: davinci: vpbe: fix build warning

Warnings were generated because of the following commit changed data type for
address pointer
195bbcac ARM: 7500/1: io: avoid writeback addressing modes for __raw_ accessors
add  __iomem annotation to fix following warnings
drivers/media/platform/davinci/vpbe_osd.c: In function ‘osd_read’:
drivers/media/platform/davinci/vpbe_osd.c:49:2: warning: passing
 argument 1 of ‘__raw_readl’ makes pointer from integer without a cast [enabled by default]
arch/arm/include/asm/io.h:104:19: note: expected ‘const volatile
 void *’ but argument is of type ‘long unsigned int’
This patch stores the ioremap_nocache() returned address in a
void __iomem * instead of a unsigned long and passes the same to
readl/writel functions which fixes the above warnings.

Signed-off-by: Lad, Prabhakar <prabhakar.lad@ti.com>
Signed-off-by: Manjunath Hadli <manjunath.hadli@ti.com>
Acked-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>