coresight: dummy: simplify the code with module_platform_driver

The init/exit() of driver only calls platform_driver_register/unregister,
it can be simpilfied with module_platform_driver.

Signed-off-by: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20230804092709.1359264-1-yangyingliang@huawei.com