espi: driver: Config spare espi vw register to OCP index

USBC port (Port 0/1/2/3) OCP (Over Current Protection) status
should be sent to PCH over eSPI VW index 0x50h. But there is
no dedicated VW register mapped to VW index 0x50h.
In this patch, configuring spare VW register SMVW06 to OCP VW
index 50h.

Signed-off-by: Diwakar C <diwakar.c@intel.com>