aries-common: Fix overlay CPU

Return CPU to cortex-a8 from cortex-a9.
This matches https://gerrit.omnirom.org/#/c/1321/

Change-Id: I106e1cdb15484894acab314a7ab0652ed04a8870
aries-common: TWRP-ify

Add TWRP flags
Add twrp.fstab

Change-Id: I7764992267599eab267e2f915e554fdbe7b831f7