device-fsl

MA-15307-1 fstab: add system item in fstab for imx8 a/b platforms

We can't delete it due to below ota build error:
"build/make/tools/releasetools/common.py", line 518, in LoadRecoveryFSTab:
   assert not d.has_key("/system") and d.has_key("/")

Revert "MA-15307 fstab: remove system item in fstab for imx8 a/b platforms"
This reverts commit d76f3030772c5cb8329f1c457dd30e507d92b515.

Change-Id: Ia59181d3465f7bd69799fa02b8d276c89e7fe8d3
Reviewed-on: http://androidsource.ap.freescale.net/project/9755
Reviewed-by: zhang sanshan <sanshan.zhang@nxp.com>