ARM: dts: msm: Change RF LDOs

LDO15 is on by default, so removed from DTS. LDO26 voltage is set to 1.8V

Change-Id: I876842dcea107eeca837a00afae36f3355cc69e7
Acked-by: Edward Rodrigues <erodrigu@qti.qualcomm.com>
Signed-off-by: Rohit Vaswani <rvaswani@codeaurora.org>