Revert "Add support for multi-user decryption"

This reverts commit 0b25b1d79b79bc4d45dfff2aaf575e10bd24ef2d.

Reason for revert: Changes need to be made to libtwrpfscrypt to include this patchset. Will cherry-pick this patch later and make necessary modifications.

Change-Id: I7601d7b820129709b05d9b4368573b6f1048de02
diff --git a/crypto/ext4crypt/Ext4Crypt.h b/crypto/ext4crypt/Ext4Crypt.h
index beb5d8f..57623e3 100644
--- a/crypto/ext4crypt/Ext4Crypt.h
+++ b/crypto/ext4crypt/Ext4Crypt.h
@@ -38,7 +38,7 @@
 bool e4crypt_unlock_user_key(userid_t user_id, int serial, const char* token, const char* secret);
 //bool e4crypt_lock_user_key(userid_t user_id);
 
-//bool e4crypt_prepare_user_storage(const char* volume_uuid, userid_t user_id, int serial, int flags);
+bool e4crypt_prepare_user_storage(const char* volume_uuid, userid_t user_id, int serial, int flags);
 //bool e4crypt_destroy_user_storage(const char* volume_uuid, userid_t user_id, int flags);
 
 bool lookup_key_ref(const std::map<userid_t, std::string>& key_map, userid_t user_id,