The efs read/write partitions will be part of the fstab.rw.efs
file and will have their own RC file to mount them.
This change allows us to identify the different partitions and
their types. It will also make easier to select different
RC files depending on the page size.
Bug: 356425337
Test: $ source build/envsetup.sh
$ lunch [zumapro]-trunk_staging-userdebug
$ m
$ ./vendor/google/tools/flashall -w
Flag: EXEMPT bugfix
Change-Id: I3eb877ecc3ccf435110ee0da4a949b44729b3bdb
