autoGood: quiet -Wimplicit-fallthrough warning

mouse.c: In function ‘autoGood’:
mouse.c:3724:12: warning: this statement may fall through [-Wimplicit-fallthrough=]
         if (mPriv->goodCount < PROBE_UNCERTAINTY/2)
            ^
mouse.c:3726:5: note: here
     default:
     ^~~~~~~

Signed-off-by: Alan Coopersmith <alan.coopersmith@oracle.com>

src/mouse.c

@@ -3727,6 +3727,7 @@ autoGood(MouseDevPtr pMse)
     case AUTOPROBE_H_VALIDATE2:
         if (mPriv->goodCount < PROBE_UNCERTAINTY/2)
             return TRUE;
+        /* FALLTHROUGH */
     default:
         return FALSE;
     }