ALSA: vmaster: Add snd_ctl_sync_vmaster() helper function

Introduce a new helper function, snd_ctl_sync_vmaster(), which updates
the slave put callbacks forcibly as well as calling the hook.  This
will be used in the upcoming patch in HD-audio codec driver for
toggling the mute in vmaster slaves.

Along with the new function, the old snd_ctl_sync_vmaster_hook() is
replaced as a macro calling with the argument hook_only=true.

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