imx: boot_mode: Add FLEXSPI boot entry

i.MX8 support FLEXSPI boot support. So add FLEXSPI boot entry.

Signed-off-by: Peng Fan <peng.fan@nxp.com>
Reviewed-by: Anatolij Gustschin <agust@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
1 file changed