staging/rdma/hfi1: Method to toggle "fast ECN" detection

Add a per port sysfs paramter to toggle cc_prescan/Fast ECN Detection and
remove the Kconfig option which was previously used to control this.

While am updating the sysfs documentation, fix the name of CCMgtA.

Reviewed-by: Arthur Kepner <arthur.kepner@intel.com>
Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Vennila Megavannan <vennila.megavannan@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>

Documentation/infiniband/sysfs.txt

@@ -78,9 +78,10 @@ HFI1
    chip_reset - diagnostic (root only)
    boardversion - board version
    ports/1/
-          CMgtA/
+          CCMgtA/
                cc_settings_bin - CCA tables used by PSM2
                cc_table_bin
+               cc_prescan - enable prescaning for faster BECN response
           sc2v/ - 32 files (0 - 31) used to translate sl->vl
           sl2sc/ - 32 files (0 - 31) used to translate sl->sc
           vl2mtu/ - 16 (0 - 15) files used to determine MTU for vl