staging: r8188eu: Fix smatch warning in os_dep/ioctl_linux.c

Smatch reports the following:
drivers/staging/rtl8188eu/os_dep/ioctl_linux.c:4891 set_group_key() warn: missing break? reassigning 'keylen'

As it suggests, there is a missing break statement.
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8188eu/os_dep/ioctl_linux.c

@@ -4884,7 +4884,6 @@ static int set_group_key(struct adapter *padapter, u8 *key, u8 alg, int keyid)
 	case _TKIP_:
 	case _TKIP_WTMIC_:
 	case _AES_:
-		keylen = 16;
 	default:
 		keylen = 16;
 	}