mediatek: also move &slot0 from dtsi down to board dts
As the referenced MTD partition is only present in the dts, also move
&slot0 down to the dts files.
Fixes: 64e9b62829 ("mediatek: remove redundant flash entry from dtsi")
Fixes: 7dbac3433f ("mediatek: add support for reyee AX3200-E5")
Signed-off-by: Daniel Golle <[email protected]>