ANDROID: mount: Add early mount for vendor and system

Add android.txt documentation from msm-4.4 kernel for early
mount of vendor and system paritions. Snapshot of android.txt
from msm-4.4 as of commit ccfb8c3db0dec ("Merge "mmc: sdhci:
Fix SDHCI_QUIRK2_IGNORE_DATATOUT_FOR_R1BCMD handling").

Change-Id: I73b982304a0a00b94aeff2822a84c267dee1c317
Signed-off-by: Prasad Sodagudi <psodagud@codeaurora.org>
Signed-off-by: Bruce Levy <blevy@codeaurora.org>