asoc: codecs: No I2C activity when EP92 is inactive

Only trigger periodic I2C telegrams when EP92 is in logical power on state.
Rely on EP92 interrupt to notice state change when in power off state.
Fix arc_enable write operation.

Change-Id: Id36f90379280ca5c60984e2ed507844418a612d7
Signed-off-by: Ralf Herz <rherz@codeaurora.org>