PCM: plug: Move fast_ops copy after slave configuration.

PCM: plug: Move fast_ops copy after slave configuration.

This is an OpenPGP/MIME signed message (RFC 2440 and 3156)
The plug plugin copies the fast_ops structure and fast_op_arg from its
slave PCM on initialization and after inserting a new plugin. This works
unless the slave PCM is also an instance of the plug plugin because plug
can change its fast_ops structure during _snd_pcm_hw_params.

Instead of copying fast_ops in snd_pcm_plug_insert_plugins wait until
the end of snd_pcm_plug_hw_params when the slave has been fully
initialized.

This fixes a crash when two instances of plug are instantiated back to
back and the format conversion plugin inserted by the second is skipped
by the first because the fast_ops pointer is not properly updated.

Signed-off-by: Takashi Iwai <tiwai@suse.de>