pds_core: Prevent possible adminq overflow/stuck condition

In the Linux kernel, the following vulnerability has been resolved:

pds_core: Prevent possible adminq overflow/stuck condition

The pds_core's adminq is protected by the adminq_lock, which prevents

more than 1 command to be posted onto it at any one time. This makes it

so the client drivers cannot simultaneously post adminq commands.

However, the completions happen in a different context, which means

multiple adminq commands can be posted sequentially and all waiting

on completion.

On the FW side, the backing adminq request queue is only 16 entries

long and the retry mechanism and/or overflow/stuck prevention is

lacking. This can cause the adminq to get stuck, so commands are no

longer processed and completions are no longer sent by the FW.

As an initial fix, prevent more than 16 outstanding adminq commands so

there's no way to cause the adminq from getting stuck. This works

because the backing adminq request queue will never have more than 16

pending adminq commands, so it will never overflow. This is done by

reducing the adminq depth to 16.