soc: fsl: cpm1: qmc: Fix unused data compilation warning

soc: fsl: cpm1: qmc: Fix unused data compilation warning

In some configuration, compilation raises warnings related to unused
data. Indeed, depending on configuration, those data can be unused.

mark those data as __maybe_unused to avoid compilation warnings.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202409071707.ou2KFNKO-lkp@intel.com/
Fixes: eb680d563089 ("soc: fsl: cpm1: qmc: Add support for QUICC Engine (QE) implementation")
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Link: https://lore.kernel.org/r/20240909121129.57067-1-herve.codina@bootlin.com
Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>