ClevoOpenBoardPkg/N1xxWU: Write PEI debug messages to SPI flash

Adds a new SerialPortLib instance to the ClevoOpenBoardPkg to support
writing debug messages to a dedicated area on SPI flash. This is to
enable closed chassis debug support on the system.

DXE and later phases after memory initialization are expected to use
USB debug.

Cc: Ankit Sinha <ankit.sinha@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Cc: Chasel Chiu <chasel.chiu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Michael Kubacki <michael.a.kubacki@intel.com>
Reviewed-by: Chasel Chiu <chasel.chiu@intel.com>
Reviewed-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
Reviewed-by: Ankit Sinha <ankit.sinha@intel.com>