drivers/iommu/omap-iopgtable.h: remove unneeded cast of void*

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>