drivers: espi: Microchip MEC172x eSPI VW initialization update

Change device tree VW routing to a form allowing overrides.
Add two new DT optional properties for specifying the reset
source and reset value of each virtual wire. Only virtual
wires that are enabled using the status property are modified.
NOTE: eSPI virtual wires are controlled in groups of 4 by
hardware. The optional reset signal source properties applies
to all four virtual wires in the group. If this field is
changed from the hardware default, it should be changed for
only one virtual wire in the group. If the property exists
in more than one wire in the group it must be set to the
same value.

Signed-off-by: Jay Vasanth <jay.vasanth@microchip.com>