MFC r222509, r222510, r222513, r222551, r222552, r222701, r222703,
and some direct modifications to minimize diffs with head.

r222509:
L2 table code. This is enough to get the T4's switch + L2 rewrite
filters working. (All other filters - switch without L2 info rewrite,
steer, and drop - were already fully-functional).

r222510:

• Specialized ingress queues that take interrupts for other ingress queues. Try to have a set of these per port when possible, fall back to sharing a common pool between all ports otherwise.
• One control queue per port (used to be one per hardware channel).
• t4_eth_rx now handles Ethernet rx only.
• sysctls to display pidx/cidx for some queues.

r222513:
Update to firmware interface 1.3.10

r222551:
Firmware device log.

r222552:
Provide hit-count with rest of the information about a filter.

r222701:
Allow lazy fill up of freelists.

r222703:
Cause backpressure (instead of dropping frames) on congestion.