ASoC: wcd9xxx: Notify RCO is ON after CLK MUX switch

When MCLK is turned off and if the CLK MUX is changed
to RCO which means that RCO is already enabled, notify
all the clients accordingly so that clock dependent
parameters can be updated.

CRs-Fixed: 776200
Change-Id: I3c6526da566572c68da7b6bd5dd5cd788ba0a5b2
Signed-off-by: Phani Kumar Uppalapati <phaniu@codeaurora.org>