MAINTAINERS: Add common-user/host/riscv to RISC-V section

Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20250422024752.2060289-1-alistair.francis@wdc.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>

MAINTAINERS

@@ -328,6 +328,7 @@ F: include/hw/char/riscv_htif.h
 F: include/hw/riscv/
 F: linux-user/host/riscv32/
 F: linux-user/host/riscv64/
+F: common-user/host/riscv*
 F: tests/functional/test_riscv*
 F: tests/tcg/riscv64/