ice: Fix DCB rebuild after reset

The function ice_dcb_rebuild had some logic
flaws in it, and also didn't differentiate
between FW and SW modes needs.

For FW flow, the willing setting was being
forced to OFF and left that way.  Unwilling
in DCB FW mode is not a supported model.

Leave the config alone and use the return value
from the set command to determine if setting the
config was successful.

The SW DCB flow does not need to need to register
for MIB change events (as they are not used in
SW mode).

Use !is_sw_lldp checks to only perform FW specific
task while in FW mode.

Also adding a reapplication of the current DCB
config after a link event.  Some NVMs are not
maintaining their DCB configs across link events.

Signed-off-by: Dave Ertman <david.m.ertman@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>