Add optional extended voltage offset range support for software and
hardware margining as defined by the USB4 specification.

If supported, it can be enabled like below:

 # cd /sys/kernel/debug/thunderbolt/ROUTER/portX/margining/
 # echo Y > optional_voltage_offset
Signed-off-by: Rene Sapiens <rene.sapiens@intel.com>
Co-developed-by: R Kannappan <r.kannappan@intel.com>
Signed-off-by: R Kannappan <r.kannappan@intel.com>
Co-developed-by: Aapo Vienamo <aapo.vienamo@linux.intel.com>
Signed-off-by: Aapo Vienamo <aapo.vienamo@linux.intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>