Currently, if the driver has control of MCLK then it remains
enabled as long as the codec is in STANDBY or above. The MCLK is
only really required in STANDBY when a 3-pole jack is inserted
and the HP detect procedure is required to run.

This patch updates the code to enable/disable the MCLK when moving
between the STANDBY and PREPARE bias level, and when a 3-pole jack
is inserted and HP detection is required, thus saving power at all
other times.
Signed-off-by: Adam Thomson <Adam.Thomson.Opensource@diasemi.com>
Signed-off-by: Mark Brown <broonie@kernel.org>