Add option to overclock to 1.6GHz

Disabled by default set CONFIG_CPU_OVERCLOCK=y in
msm8226_mmi_defconfig to enable
Change-Id: I0aced0e13c1d97b72ad26cdd10178440b0da9f1f

Conflicts:
	arch/arm/boot/dts/msm8226.dtsi
	arch/arm/configs/msm8226_mmi_defconfig