ASoC: wcd9335: Add support for digital core power collapse

When no audio use-cases are active, codec digital core
can be put into power collapse to reduce the power consumption
during codec stand-by. Add support to put core into power
collapse and remove out of the collapse when audio use-cases
are triggered.

Change-Id: Ib72b72239712d1b20542950f05b698647edcb9fa
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>