Remove unused variable.

This doesn't fire until libc++ is updated. Presumably this used to
have some side effect that it shouldn't have had.

Test: m checkbuild
Bug: None
Change-Id: Ic60e0885799143efde23b91b05e5c1afd8356ae9
diff --git a/boot_control.cpp b/boot_control.cpp
index e8a6421..2452412 100644
--- a/boot_control.cpp
+++ b/boot_control.cpp
@@ -527,7 +527,6 @@
 	int rc = -1;
 	int is_ufs = gpt_utils_is_ufs_device();
 	map<string, vector<string>>::iterator map_iter;
-	vector<string>::iterator string_iter;
 
 	if (boot_control_check_slot_sanity(module, slot)) {
 		ALOGE("%s: Bad arguments", __func__);