gpio: msm: Remove unused driver

Remove this driver now that Bjorn has introduced a pinctrl driver
for msm8660 and the dts files have been updated with the pinctrl
compatibles.

Cc: Andy Gross <agross@codeaurora.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@sonymobile.com>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>