ARM: omap2: fix missing include

ARM: omap2: fix missing include

commit 3db1db66dad7
"gpio: don't include module.h in shared driver header"
removed <linux/module.h> from the <linux/gpio/driver.h> header.

It seems arch/arm/mach-omap2/board-rx51-peripherals.c
is using __initdata_or_module from <linux/module.h> through
<linux/gpio.h> to <linux/gpio/driver.h>, so break this dependency
so that we get a clean compile.

Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Tony Lindgren <tony@atomide.com>
Fixes: 3db1db66dad7 ("gpio: don't include module.h in shared driver header")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>