On low power turn off rather than rebooting to allow device to charge

The code was using encrypted_upto == 0 as an indicator that encryption
has succeeded. This meant that if no encryption happened, we would reboot
continually.

We now set encrypted_upto to fs_size when encryption is complete.

Also don't start to encrypt unless we are at 10% power. Stop when we
get to 5% power. This should lead to partial encryptions only very
rarely.

Bug: 15513202
Change-Id: I6214d78579d1fbbe2f63ee8862473d86a89d29b3
diff --git a/CheckBattery.h b/CheckBattery.h
index a7bff34..dd11ba9 100644
--- a/CheckBattery.h
+++ b/CheckBattery.h
@@ -21,7 +21,8 @@
 extern "C" {
 #endif
 
-int is_battery_ok();
+int is_battery_ok_to_start();
+int is_battery_ok_to_continue();
 
 #ifdef __cplusplus
 }