soc: fsl: cpm1: qmc: Remove no more needed checks from qmc_check_chans()

The newly introduced qmc_chan_setup_tsa* functions check that the
channel entries are not already used.
These checks are also performed by qmc_check_chans() and are no more
needed.

Remove them from qmc_check_chans().

Signed-off-by: Herve Codina <herve.codina@bootlin.com>
Reviewed-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/r/20231205152116.122512-11-herve.codina@bootlin.com