net: macb: remove bp->queue_mask

net: macb: remove bp->queue_mask

The low 16 bits of GEM_DCFG6 tell us which queues are enabled in HW. In
theory, there could be holes in the bitfield. In practice, the macb
driver would fail if there were holes as most loops iterate upon
bp->num_queues. Only macb_init() iterated correctly.

 - Drop bp->queue_mask field.
 - Error out at probe if a hole is in the queue mask.
 - Rely upon bp->num_queues for iteration.
 - As we drop the queue_mask probe local variable, fix RCT.
 - Compute queue_mask on the fly for TAPRIO using bp->num_queues.

Signed-off-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://patch.msgid.link/20251014-macb-cleanup-v1-10-31cd266e22cd@bootlin.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>