ARM: dts: msm: Correct parent regulator for sdxlemur VDD_CX_LEVEL_AO

The VDD_CX_LEVEL_AO regulator node currently propagates its vote to
VDD_MxA during Linux suspend. Correct this to make the node propagate it
to VDD_MXA_LEVEL_AO so that APPS can vote for "OFF" in the absence of
any other consumers.

Change-Id: I37a60204a691841182ed7b5517a583c9d02d96c9