dts: npcx: add soc-if node and move interface phandles into it.

This CL moves the phandles which don't contain 'reg' prop. from 'soc' to
'soc-if' node since they are the interface phandles only. It also
prevents "missing or empty reg/ranges property" warning messages.

Signed-off-by: Mulin Chao <mlchao@nuvoton.com>