[SCSI] qla2xxx: Allow the user the option of disabling iIDMA.

iIDMA support requires the driver issue several additional
fabric-managegment (FM) commands per port discovered during SNS
scanning -- GFPN (Get Fabric Port Name) and GPSC (Get Port Speed
Capabilities).  It has been found during testing that some
switches do not respond as *well* as expected to these commands
(silence -- no ACC nor BS_RJT).  So, to handle such conditions,
allow the user the ability to indirectly disable the FM commands
by disabling iIDMA with the ql2xiidmaenable module-parameter.

Signed-off-by: Andrew Vasquez <andrew.vasquez@qlogic.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>