gpio: omap: omap_gpio_show_rev is not __init

The probe function calls omap_gpio_show_rev(), which on most
compilers is inlined, but on the old gcc-4.6 is not, causing
a valid warning about the incorrect __init annotation:

WARNING: vmlinux.o(.text+0x40f614): Section mismatch in reference from the function omap_gpio_probe() to the function .init.text:omap_gpio_show_rev()
The function omap_gpio_probe() references
the function __init omap_gpio_show_rev().
This is often because omap_gpio_probe lacks a __init
annotation or the annotation of omap_gpio_show_rev is wrong.

This removes the __init.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Santosh Shilimkar <ssantosh@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>