apm821xx: fix dtc compiler warnings for MX60(W) and MR24's dts files

apm821xx: fix dtc compiler warnings for MX60(W) and MR24's dts files

This patch fixes some of the dtc warnings:

MR24:
"reg" property in [...]mdio/phy@1 has invalid length (4 bytes)
Node [...]button@1 has a unit name, but no reg property
Relying on default #address-cells value for [...]phy@1
Relying on default #size-cells value for [...]phy@1

MX60(W):
Node [..]nand/all has a reg or ranges property, but no unit name
Node [..]button@1 has a unit name, but no reg property

Signed-off-by: Christian Lamparter <[email protected]>
(backported from c417aee9f146f26cd12642138bc0cedf5950a59a)