log: don't re-initialize the log level in pw_init()
This allows setting the log level without setting PIPEWIRE_DEBUG prior to pw_init(). Setting it after is also possible, but we get to miss some messages that are printed from pw_init()
This allows setting the log level without setting PIPEWIRE_DEBUG prior to pw_init(). Setting it after is also possible, but we get to miss some messages that are printed from pw_init()