npcx: scfg: psl: cleanup unused functions and DT files

Clean up unused psl functions in scfg.c, unused DT macros, unused psl DT
nodes and related yaml files. Currently, PSL pad configurations are made
by pinctrl mechanism. Please refer
https://issuetracker.google.com/234861079

 for more detail.

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