eSPI: NPCX/ITE: Enable conditional virtual wire valid bit check

On the new Intel SoC, the "Valid" bit of the Virtual Wire is set only for
Virtual Wires that undergo changes. This behavior differs from previous
generations. Therefore, to maintain backward compatibility, a conditional
check for the virtual wire valid bit is added for processing the virtual
wire level.

Signed-off-by: Vijay Hiremath <vijay.p.hiremath@intel.com>