As suggested by Russell King - ARM Linux <linux@arm.linux.org.uk>,
there's no need to keep local prototypes in non-local headers.

Add mach-omap1/common.h and mach-omap2/common.h and move the
local prototypes there from plat/common.h and mach/omap4-common.h.
Signed-off-by: NTony Lindgren <tony@atomide.com>
Signed-off-by: NRussell King <rmk+kernel@arm.linux.org.uk>