roc-rk3399-pc: Mark default env from SPI

Mark the default U-Boot environment as SPI flash since
this is an on board flash device.

Updated env offset, size in contrast with default since
the U-Boot proper has to start from 384K.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
3 files changed