ARM: dts: msm: increase vddio voltage for hdk r66451 dsi panel

Set vddio voltage to 1.86v for hdk, since some of hdk dsi panel's
vddio voltage has a larger drop, they could not work well on 1.8v.

Change-Id: Id7dde6d1ffee9cab853b23b05c1c345e829aea87