hw/timer/cmsdk-apb-dualtimer: Add missing 'break' statements

Add 'break' statements missing from a switch in the APB dual-timer
write function. Spotted by Coverity as CID 1395626 and 1395633.
Reported-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>
Reviewed-by: NPhilippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20180924123122.14549-1-peter.maydell@linaro.org

hw/timer/cmsdk-apb-dualtimer.c

@@ -296,9 +296,11 @@ static void cmsdk_apb_dualtimer_write(void *opaque, hwaddr offset,
         case A_TIMERITCR:
             s->timeritcr = value & R_TIMERITCR_VALID_MASK;
             cmsdk_apb_dualtimer_update(s);
+            break;
         case A_TIMERITOP:
             s->timeritop = value & R_TIMERITOP_VALID_MASK;
             cmsdk_apb_dualtimer_update(s);
+            break;
         default:
         bad_offset:
             qemu_log_mask(LOG_GUEST_ERROR,