soc/fsl/qbman: Fixup qman_shutdown_fq()

When shutting down a FQ on a dedicated channel only the
SW portal associated with that channel can dequeue from it.
Make sure the correct portal is use.

Signed-off-by: Roy Pledge <roy.pledge@nxp.com>
Signed-off-by: Li Yang <leoyang.li@nxp.com>