cpm_uart: Disable CPM udbg when re-initing CPM uart, even if not the console.

Previously, if udbg was using the CPM uart, and the normal CPM uart driver
was enabled, but the console was directed elsewhere, udbg would not be
stopped prior to initialization.  This resulted in udbg hanging forever
waiting for the CPM to process a descriptor.

Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>