gpio_msm: Move Qualcomm v6 MSM driver into drivers

Migrate the driver for the v6-based MSM chips into drivers/gpio.  The
driver is unchanged, only moved.

Change-Id: I03ba597b95b4d62b42da112a8efac88d67aa40f9
Signed-off-by: David Brown <davidb@codeaurora.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Nicolas Pitre <nicolas.pitre@linaro.org>