ARM: dts: msm: Update PCIe LDO clock from CXO to CXO_A

LDO votes CXO clock in WLAN IMPS mode which causes
CXO clock is always turned on, So changing PCIe LDO
clock from CXO to CXO_A.

Change-Id: I6b0ad98be2017e58e133751baa3febd69c77e83d