wcte43x: Do not grab reglock in handle_transmit/handle_receive.

If the driver is loaded with vpmsupport=0, then it was possible to create a
deadlock situation since the call into __dahdi_ec_chunk might then try to grab
the channel lock while already holding the reglock.

The purpose of grabbing reglock in the DMA routines was to protect the channel
array, which can be changed when linemode is changing. So instead, we'll
completely mask off that interrupt line from all CPUs when potentially changing
the channel array.

Signed-off-by: Shaun Ruffell <sruffell@digium.com>
wcte43x: Remove 'dcxo' debug attribute.

Removes another bit of debugging instrumentation that I let slip through.

Signed-off-by: Shaun Ruffell <sruffell@digium.com>