Defer to register acomp eld notifier until hdmi audio driver
is fully ready.

After registering eld notifier, gfx driver can use this
callback function to notify audio driver the monitor
connection event. However this action may happen when
audio driver is adding the pins or doing other initialization.
This is not always safe, however. For example, using
per_pin->lock before the lock is initialized.

Let's register the eld notifier after the initialization is done.
Signed-off-by: Libin Yang <libin.yang@linux.intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>