The local variable 'msm_gpio' is used only in this file.
Fix the following sparse warning:

drivers/gpio/gpio-msm-v2.c:109:21: warning: symbol 'msm_gpio' was not declared. Should it be static?
Signed-off-by: NJingoo Han <jg1.han@samsung.com>
Signed-off-by: NLinus Walleij <linus.walleij@linaro.org>