ENGR00179150 MX6Q_ARM2 HAB Boot : avoid uImage authentication on un-fused chip

Before running authentication on uImage in DDR, u-boot first check if
SEC_CONFIG[1] (OTP_CFG5[1]) is burned. If so, it means the chip is in
secure configuration, the authentication continues; if not, the chip
in not in secure configuration, just bypass the authentication

Signed-off-by: Eric Sun <jian.sun@freescale.com>