stdlib: Add missing @overrides to RISCVBoard

Change-Id: I6879c9744c28038c5d40984785f2f502a2fd1c5a
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/52185
Reviewed-by: Bobby R. Bruce <bbruce@ucdavis.edu>
Maintainer: Bobby R. Bruce <bbruce@ucdavis.edu>
Tested-by: kokoro <noreply+kokoro@google.com>

src/python/gem5/components/boards/riscv_board.py

@@ -183,9 +183,11 @@ class RiscvBoard(AbstractBoard, KernelDiskWorkload):
     def get_io_bus(self) -> IOXBar:
         return self.iobus
 
+    @overrides(AbstractBoard)
     def has_coherent_io(self) -> bool:
         return True
 
+    @overrides(AbstractBoard)
     def get_mem_side_coherent_io_port(self) -> Port:
         return self.iobus.mem_side_ports