The QUICC Engine (QE) QMC can use a firmware to have the QMC working in
'soft-qmc' mode.

Handle this optional 'soft-qmc' firmware.
Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/20240808071132.149251-36-herve.codina@bootlin.comSigned-off-by: Christophe Leroy <christophe.leroy@csgroup.eu>