regmap: Add soundwire bus support

Add soundwire bus support to regmap. This change enables
codec drivers using soundwire hardware interface to use
regmap interface for register read/write functionality.

Change-Id: I668a99f7d0561e9523a1abfa276f2dcdbb39d1f1
Signed-off-by: Sudheer Papothi <spapothi@codeaurora.org>
Signed-off-by: Banajit Goswami <bgoswami@codeaurora.org>