scsi: lpfc: cleanup: convert eq_delay to usdelay

Review of the eq coalescing logic showed the code was a bit fragmented.
Sometimes it would save/set via an interrupt max value, while in others it
would do so via a usdelay. There were also two places changing eq delay,
one place that issued mailbox commands, and another that changed via
register writes if supported.

Clean this up by:

 - Standardizing the operation of lpfc_modify_hba_eq_delay() routine so
   that it is always told of a us delay to impose. The routine then chooses
   the best way to set that - via register or via mbx.

 - Rather than two value types stored in eq->q_mode (usdelay if change via
   register, imax if change via mbox) - q_mode always contains usdelay.
   Before any value change, old vs new value is compared and only if
   different is a change done.

 - Revised the dmult calculation. dmult is not set based on overall imax
   divided by hardware queues - instead imax applies to a single cpu and
   the value will be replicated to all cpus.

Signed-off-by: Dick Kennedy <dick.kennedy@broadcom.com>
Signed-off-by: James Smart <jsmart2021@gmail.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>