Current code handles the CPM1 version of QMC and initialize the QMC used
SCC. The QUICC Engine (QE) version uses an UCC (Unified Communication
Controllers) instead of the SCC (Serial Communication Controllers) used
in the CPM1 version. These controllers serve the same purpose and are
used in the same way but their inializations are slightly different.

In order to prepare the support for QE version of QMC, introduce
qmc_init_xcc() to initialize theses controllers (UCC in QE and SCC in
CPM1) and isolate the CPM1 specific SCC initialization in a specific
function.

Also introduce qmc_exit_xcc() for consistency to revert operations done
in qmc_init_xcc().
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/20240808071132.149251-28-herve.codina@bootlin.comSigned-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>