i40e/i40evf: Add set_fc and init of FC settings

Add function set_fc to set the requested FC mode. This patch also
adds the init of FC setting to get_link_info and replaces the init
code to set FC off by default in main. Also adds i40e_set_phy_config
to support this.

Change-ID: I7b25bbaec81f15777137ab324a095f916e44351d
Signed-off-by: Catherine Sullivan <catherine.sullivan@intel.com>
Tested-by: Jim Young <jamesx.m.young@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>