This is the same approach as done for AP_HAL_Linux in e3d78b8 ("AP_HAL_Linux:
fix passing callback to member function"). It fixes the following warnings:
ardupilot/libraries/AP_HAL_PX4/Scheduler.cpp: In member function 'virtual void PX4::PX4Scheduler::init(void*)':
ardupilot/libraries/AP_HAL_PX4/Scheduler.cpp:55:95: warning: converting from 'void* (PX4::PX4Scheduler::*)()' to 'pthread_startroutine_t {aka void* (*)(void*)}' [-Wpmf-conversions]
pthread_create(&_timer_thread_ctx, &thread_attr, (pthread_startroutine_t)&PX4::PX4Scheduler::_timer_thread, this);
^
ardupilot/libraries/AP_HAL_PX4/Scheduler.cpp:65:94: warning: converting from 'void* (PX4::PX4Scheduler::*)()' to 'pthread_startroutine_t {aka void* (*)(void*)}' [-Wpmf-conversions]
pthread_create(&_uart_thread_ctx, &thread_attr, (pthread_startroutine_t)&PX4::PX4Scheduler::_uart_thread, this);
^
ardupilot/libraries/AP_HAL_PX4/Scheduler.cpp:75:92: warning: converting from 'void* (PX4::PX4Scheduler::*)()' to 'pthread_startroutine_t {aka void* (*)(void*)}' [-Wpmf-conversions]
pthread_create(&_io_thread_ctx, &thread_attr, (pthread_startroutine_t)&PX4::PX4Scheduler::_io_thread, this);
^
ardupilot/libraries/AP_HAL_PX4/Scheduler.cpp:85:100: warning: converting from 'void* (PX4::PX4Scheduler::*)()' to 'pthread_startroutine_t {aka void* (*)(void*)}' [-Wpmf-conversions]
pthread_create(&_storage_thread_ctx, &thread_attr, (pthread_startroutine_t)&PX4::PX4Scheduler::_storage_thread, this);
ardupilot/libraries/AP_HAL_PX4/NSHShellStream.cpp: In member function 'void PX4::NSHShellStream::start_shell()':
ardupilot/libraries/AP_HAL_PX4/NSHShellStream.cpp:83:99: warning: converting from 'void (PX4::NSHShellStream::*)()' to 'pthread_startroutine_t {aka void* (*)(void*)}' [-Wpmf-conversions]
pthread_create(&shell_thread_ctx, &thread_attr, (pthread_startroutine_t)&PX4::NSHShellStream::shell_thread, this);
^
The argument in init() is not used by any implementation. Add a second
method without it so the HAL implementation can used it instead. Later
the unused method will be removed.
