fstab: Run fsck on /persist too.

This partition gets no activity, but it can still get corrupted by
unclean shutdowns; fsck all the things

Change-Id: I60c08b5d3157e582c96f5131fd0195dd591f6fc1
Merge remote-tracking branch 'SlimRoms_device_oneplus_bacon/kk4.4' into kk4.4