ASoC: DaVinci I2S updates

This resyncs the DaVinci I2S code with the version in the DaVinci
tree.  The behavioral change uses updated clock interfaces which
recently merged to mainline.  Two other changes include adding a
comment on the ASP/McBSP/McASP confusion, and dropping pdev->id in
order to support more boards than just the DM644x EVM.

Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>