ARM: dts: msm: add DT entries for LDO mode, byte and pixel clk for 8939

Add DT entries for the MDSS DSI byte clock and pixel clock on
msm8939. This will enable the DSI drivers in successfully
registering the DSI byte and pixel clocks.

Also on msm8939, the DSI PHY regulator operates in LDO mode. Add
DT entries to enable LDO mode by default and program the DSI
registers with the corresponding LDO mode values.

Change-Id: I8baf0c300cb1d1a44c5e5866a6557793b8c5334a
Signed-off-by: Padmanabhan Komanduru <pkomandu@codeaurora.org>
Signed-off-by: Radhika Ranjan Soni <rrsoni@codeaurora.org>