bhyve nvme: Remove redundant AER Limit checks

[chuck]

Summary

The NVMe emulation checked if the Asynchronous Event Request Limit
(a.k.a AERL) would be exceeded in pci_nvme_aer_add(), but this function
is only called from nvme_opc_async_event_req() which also checks for
exceeding the AERL.

While in the neighborhood, fix / enhance the debug logging.

Tested by:
MFC after: 2 weeks

[allanjude]

Reviewed By: allanjude

[imp]

I don't see the 'while in the area' changes, so omit that from the final commit message.

[chuck]

In D33570#759866, @imp wrote:

I don't see the 'while in the area' changes, so omit that from the final commit message.

Good catch. Fixed.