ALSA: core: modify, rename and export create_subdir API

Modify create_subdir API, so that it can create a subdir
under a given parent directory and then register the info
entry. Also rename and export the API so that it can be
used to expose ID and version related information.

Change-Id: Id8a29ce575199ccee009619f9a6692e59964df50
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>
Signed-off-by: Meng Wang <mwang@codeaurora.org>