cxgbe(4): Expanded interrupt handling for T7

• Catch up with the new cause/perr registers. The high level approach is the same but the T7 has an extra top level INT_CAUSE concentrator and a PERR_CAUSE concentrator with a changed layout.

• Add various flags to control the interrupt handlers' behavior.

• Implement a t4_intr_clear that internally use the slow handler as an iterator over known cause/perr registers. This lets the driver clear all of the interrupt sources that it knows about. The firmware sets up the interrupt enables and clears the causes normally so this call should be redundant.

MFC after: 1 week
Sponsored by: Chelsio Communications