Define per-queue locks for protecting queue state and event pool sent/free
lists. The evt list lock is initially redundant but it allows the driver to
be modified in the follow-up patches to relax the queue locking around
submissions and completions.

Link: https://lore.kernel.org/r/20210106201835.1053593-4-tyreld@linux.ibm.comReviewed-by: Brian King <brking@linux.vnet.ibm.com>
Signed-off-by: Tyrel Datwyler <tyreld@linux.ibm.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>