ALSA: Jack: handle jack embedded kcontrol creating within ctljack

This patch adds a static method get_available_index() to
allocate the index of new jack kcontrols and also adds
jack_kctl_name_gen() which is used to ensure compatibility
with jack naming by removing " Jack" from some incorrectly
passed names.

Signed-off-by: Jie Yang <yang.jie@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>