dts: scobc_a1: Add FPGA related definitions

Adds SC-OBC Module A1 FPGA System Register and System Monitor
definitions to DTS.

  - System Register
    Registers for system control of SC-OBC Module A1
    Link: https://sc-obc-fpga-technical-reference-manual.readthedocs.io/ja/latest/#org19067cd

  - System Monitor
    Module for monitoring the SC-OBC Module A1 system
    Link: https://sc-obc-fpga-technical-reference-manual.readthedocs.io/ja/latest/#org8832978



Signed-off-by: Takuya Sasaki <takuya.sasaki@spacecubics.com>