ASoC: wcd_cpe_core: Add support for CPE power collapse

When CPE (Codec Processing Engine) is not being used, it can be switched
to low power mode and the clocks to CPE can be turned off. This will
save power consumption by CPE when CPE is not being used. Add support
for CPE power collapse.

Change-Id: I3610e3037f3f17ac5dccc8b8d76cb3a6655aaff7
Signed-off-by: Bhalchandra Gajare <gajare@codeaurora.org>