ARM: dts: msm: set device reference clock setting to 19.2 MHz for MSMSKUNK

MSMSKUNK platform provides 19.2 MHz device reference clock to UFS device
hence this change updates the UFS host setting (dev-ref-clk-freq) to
reflect this.

Change-Id: I61ee13b670168afcf578125f7be56b50a46f3a65
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>