wifi: ath11k: 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: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://lore.kernel.org/r/20230804091255.1347178-1-yangyingliang@huawei.com