arch/arm/mach-shmobile/board-ag5evm.c: included linux/dma-mapping.h twice

arch/arm/mach-shmobile/board-ag5evm.c: included 'linux/dma-mapping.h'
twice, remove the duplicate.

Signed-off-by: Danny Kukawka <danny.kukawka@bisect.de>
Signed-off-by: Paul Mundt <lethal@linux-sh.org>