KabylakeOpenBoardPkg/PeiSerialPortLibSpiFlash: Update for new SPI PPI API

REF:https://bugzilla.tianocore.org/show_bug.cgi?id=3307



Updates usage of gPchSpiPpiGuid to use the new interface that
identifies SPI flash regions by GUID.

Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Signed-off-by: Michael Kubacki <michael.kubacki@microsoft.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>
Reviewed-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
Tested-by: Benjamin Doron <benjamin.doron00@gmail.com>