[factory reset protection] Add /persistent to fstab

This is required so the recovery kernel can wipe the
partition in case the feature is disabled by
Settings > Developer options > Enable OEM unlock.

Bug: 18136196
Change-Id: I033033e440ecab5afdffcdbd0f17dcc8984a7df5
diff --git a/fstab.shamu b/fstab.shamu
index 54018cb..83c4af9 100644
--- a/fstab.shamu
+++ b/fstab.shamu
@@ -24,3 +24,4 @@
 /dev/block/platform/msm_sdcc.1/by-name/aboot        /aboot          emmc    defaults                                                        defaults
 /dev/block/platform/msm_sdcc.1/by-name/versions     /versions       emmc    defaults                                                        defaults
 /dev/block/platform/msm_sdcc.1/by-name/logo         /logo           emmc    defaults                                                        defaults
+/dev/block/platform/msm_sdcc.1/by-name/frp          /persistent     emmc    defaults                                                        defaults