fix mountpoint test to not prevemt mkfs_xxx from making image in any file

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/include/libbb.h b/include/libbb.h
index 936d98a..c7b4de1 100644
--- a/include/libbb.h
+++ b/include/libbb.h
@@ -995,7 +995,7 @@
 
 #ifdef HAVE_MNTENT_H
 extern int match_fstype(const struct mntent *mt, const char *fstypes) FAST_FUNC;
-extern struct mntent *find_mount_point(const char *name) FAST_FUNC;
+extern struct mntent *find_mount_point(const char *name, int subdir_too) FAST_FUNC;
 #endif
 extern void erase_mtab(const char * name) FAST_FUNC;
 extern unsigned int tty_baud_to_value(speed_t speed) FAST_FUNC;