fastboot: remove retries on invalid IO iterator in OSX

When IOServiceGetMatchingServices returns an invalid
iterator, IOIteratorReset doesn't help. Break the loop
to prevent being stuck in the reset loop forever.
This should be fine as the open_device() call in the
upper layer is already doing retries.

Bug: 286495045
Test: fastboot update
Change-Id: Ia58fa9285640be34aa22cd77e4f58cc9092679a4

fastboot/usb_osx.cpp

@@ -436,12 +436,7 @@ static int init_usb(ifc_match_func callback, std::unique_ptr<usb_handle>* handle
 
     for (;;) {
         if (! IOIteratorIsValid(iterator)) {
-            /*
-             * Apple documentation advises resetting the iterator if
-             * it should become invalid during iteration.
-             */
-            IOIteratorReset(iterator);
-            continue;
+            break;
         }
 
         io_service_t device = IOIteratorNext(iterator);