thunderbolt: Add missing usb4_port_sb_read() to usb4_port_sw_margin()

thunderbolt: Add missing usb4_port_sb_read() to usb4_port_sw_margin()

Synchronize the operation completion by reading back the software
margining operation completion metadata into margining->results.

Signed-off-by: Aapo Vienamo <aapo.vienamo@linux.intel.com>
Co-developed-by: R Kannappan <r.kannappan@intel.com>
Signed-off-by: R Kannappan <r.kannappan@intel.com>
Co-developed-by: Rene Sapiens <rene.sapiens@intel.com>
Signed-off-by: Rene Sapiens <rene.sapiens@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>