usb/hcd-ehci: Remove redundant statements

The "again" assignment is meaningless before g_assert_not_reached.
In addition, the break statements no longer needs to be after
g_assert_not_reached.

Clang static code analyzer show warning:
hw/usb/hcd-ehci.c:2108:13: warning: Value stored to 'again' is never read
            again = -1;
            ^       ~~

Reported-by: Euler Robot <euler.robot@huawei.com>
Signed-off-by: Chen Qun <kuhn.chenqun@huawei.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Message-Id: <20200226084647.20636-13-kuhn.chenqun@huawei.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>

hw/usb/hcd-ehci.c

@@ -1301,7 +1301,6 @@ static void ehci_execute_complete(EHCIQueue *q)
         /* should not be triggerable */
         fprintf(stderr, "USB invalid response %d\n", p->packet.status);
         g_assert_not_reached();
-        break;
     }
 
     /* TODO check 4.12 for splits */
@@ -2105,9 +2104,7 @@ static void ehci_advance_state(EHCIState *ehci, int async)
 
         default:
             fprintf(stderr, "Bad state!\n");
-            again = -1;
             g_assert_not_reached();
-            break;
         }
 
         if (again < 0 || itd_count > 16) {