gpio_msm: using for_each_set_bit to simplify the code

Using for_each_set_bit() to simplify the code.

spatch with a semantic match is used to found this.
(http://coccinelle.lip6.fr/

)

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: David Brown <davidb@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>