ext4_utils: add declaration for ext4_bg_has_super_block()

Add a declaration for ext4_bg_has_super_block() so that the
encrypt-in-place code in vold can use it to determine whether a backup
superblock is present in a block group.

Bug: 162479411
Bug: 161871210
Merged-In: Ic090bf4e88193b289b04c5254ddf661ef40b037e
Change-Id: Ic090bf4e88193b289b04c5254ddf661ef40b037e
diff --git a/ext4_utils/include/ext4_utils/ext4_utils.h b/ext4_utils/include/ext4_utils/ext4_utils.h
index 2715614..cf65787 100644
--- a/ext4_utils/include/ext4_utils/ext4_utils.h
+++ b/ext4_utils/include/ext4_utils/ext4_utils.h
@@ -131,7 +131,7 @@
 u64 get_block_device_size(int fd);		// recovery
 int is_block_device_fd(int fd);			// wipe.c
 u64 get_file_size(int fd);			// fs_mgr
-
+int ext4_bg_has_super_block(int bg);
 int read_ext(int fd, int verbose);		// vold
 
 #ifdef __cplusplus