ARM: dts: msm: add gpio_key VOL_UP button on SDM660

Add pinctrl configurations for volume up button which utilize PM660L
GPIO 7.Add gpio_key devices for this button on SDMM660.

Change-Id: I53cb73ad71c92cdde50c9257f7d4a8fceaa3023f
Signed-off-by: Asha Magadi Venkateshamurthy <amagad@codeaurora.org>