docs/devel/reset: Update to new API for hold and exit phase methods

docs/devel/reset: Update to new API for hold and exit phase methods

Update the reset documentation's example code to match the new API
for the hold and exit phase method APIs where they take a ResetType
argument.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Luc Michel <luc.michel@amd.com>
Message-id: 20240412160809.1260625-6-peter.maydell@linaro.org