ARM: OMAP2+: Remove unnecesary include in GPMC driver

The GPMC driver includes arch/arm/mach-omap2/common.h but
does not use anything on that header so it can be removed.

Signed-off-by: Javier Martinez Canillas <javier.martinez@collabora.co.uk>
Signed-off-by: Tony Lindgren <tony@atomide.com>