hw/riscv: spike: Remove misleading comments

PLIC is not included in the 'spike' machine.

Signed-off-by: Bin Meng <bmeng@tinylab.org>
Reviewed-by: Wilfred Mallawa <wilfred.mallawa@wdc.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20221211030829.802437-5-bmeng@tinylab.org>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

hw/riscv/spike.c

@@ -8,7 +8,6 @@
  *
  * 0) HTIF Console and Poweroff
  * 1) CLINT (Timer and IPI)
- * 2) PLIC (Platform Level Interrupt Controller)
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms and conditions of the GNU General Public License,