ARM: dts: msm: Add fixed regulator for AVDD in SDM845

Same gpio 8 is used by both front and iris camera
for AVDD. So, add a fixed regulator node for AVDD.

Change-Id: I5613925dd63536421b9b27d20de025951e7024f8
Signed-off-by: Vivek Veenam <vveenam@codeaurora.org>