ARM: dts: hammerhead: Change i2c clock-rate to 19.2 MHz

Referenced CAF: https://www.codeaurora.org/cgit/quic/la/kernel/msm/commit/arch/arm/boot/dts/msm8974.dtsi?h=kk_3.5&id=2762366bdeb1d2d3bb43ffb21ad3a0908d51551e