ARM: imx: Decode ECSPI env location from i.MX8M ROMAPI tables

Decode ECSPI boot device in env_get_location() from i.MX8M ROMAPI tables.
This is necessary to correctly identify env is in SPI NOR when the system
boots from SPI NOR attached to ECSPI.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Fabio Estevam <festevam@denx.de>
Cc: Peng Fan <peng.fan@nxp.com>
Cc: Stefano Babic <sbabic@denx.de>
Reviewed-by: Fabio Estevam <festevam@denx.de>