ARM: dts: msm: Early mount of vendor partition for SDM855

Add support to early mount vendor partition from device tree. This is
required so that vendor modules can be loaded during early-init.

Change-Id: Ic92c6384fe8237e8090c3322073cb6cd3c40e60e
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>