soc: fsl: qbman: Add helper for sanity checking cgr ops

This breaks out/combines get_affine_portal and the cgr sanity check in
preparation for the next commit. No functional change intended.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Acked-by: Camelia Groza <camelia.groza@nxp.com>
Signed-off-by: David S. Miller <davem@davemloft.net>