imx8m: workaround ROM serror

imx8m: workaround ROM serror

ROM SError happens on two cases:

1. ERR050342, on iMX8MQ HDCP enabled parts ROM writes to GPV1 register, but
when ROM patch lock is fused, this write will cause SError.

2. ERR050350, on iMX8MQ/MM/MN, when the field return fuse is burned, HAB
is field return mode, but the last 4K of ROM is still protected and cause
SError.

Since ROM mask SError until ATF unmask it, so then ATF always meets the
exception. This patch works around the issue in SPL by enabling SPL
Exception vectors table and the SError exception, take the exception
to eret immediately to clear the SError.

Signed-off-by: Ye Li <ye.li@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>