ARM: dts: msm: enable AHB2PHY_WEST clock during DP PLL programming

AHB2PHY_WEST clock needs to be enabled to program Display Port PLL
registers for SM6150. Add the clock node for this in the SM6150 DP
PLL node to take care of this.

Change-Id: I93b778bcc05639856a2b31faed1d0d8c67e4e1aa
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>