MAINTAINERS: Cover RISC-V HTIF interface

MAINTAINERS: Cover RISC-V HTIF interface

The HTIF interface is RISC-V specific, add
it within the MAINTAINERS section covering
hw/riscv/.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
Message-ID: <20241129154304.34946-2-philmd@linaro.org>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>