ARM: dts: uniphier: simplify support-card node structure

This device hierarchy is needlessly complex.

Remove the support-card node level, and move the ethernet and serial
nodes right under the system-bus node.

This also fixes the following warning from 'make ARCH=arm dtbs_check':

  support-card@1,1f00000: $nodename:0: 'support-card@1,1f00000' does not match '^(bus|soc|axi|ahb|apb)(@[0-9a-f]+)?$'

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>