riscv: dts: microchip: mpfs: Fix clock controller node

Fix the device node for the clock controller:
  - Remove bogus "reg-names" property,
  - Remove unneeded "clock-output-names" property.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Tested-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>