ARM: dts: aspeed: wedge400: Fix FMC flash0 layout

Update "data0" partition's size from 8MB to 4MB to fix "partition data0
extends beyond the end of device" warning at bootup time.

Signed-off-by: Tao Ren <rentao.bupt@gmail.com>
Reviewed-by: Joel Stanley <joel@jms.id.au>
Link: https://lore.kernel.org/r/20201110072159.7941-1-rentao.bupt@gmail.com


Signed-off-by: Joel Stanley <joel@jms.id.au>