ASoC: McPDM: Update channels management to link UL and DL

Due to HW bug on McPDM CTRL register both UL and DL channels need
to be configure at the same time. If the channels are not
configured at the same time so side effect can be muting in
Uplink or loud noise in downlink during stress test transition
between UL and Downlink. Each time McPDM is started both UL and
DL channels are enabled to work around the problem.
This patch is also remote the DC OFFSET interface as it is not
working correctly and connot be used. So there is no need for the
driver to configure it.

Signed-off-by: Sebastien Guiriec <s-guiriec@ti.com>