riscv_trigger_init() had been called on reset events that can happen
several times for a CPU and it allocated timers for itrigger. If old
timers were present, they were simply overwritten by the new timers,
resulting in a memory leak.

Divide riscv_trigger_init() into two functions, namely
riscv_trigger_realize() and riscv_trigger_reset() and call them in
appropriate timing. The timer allocation will happen only once for a
CPU in riscv_trigger_realize().

Fixes: 5a4ae64c ("target/riscv: Add itrigger support when icount is enabled")
Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: LIU Zhiwei <zhiwei_liu@linux.alibaba.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-ID: <20230818034059.9146-1-akihiko.odaki@daynix.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>