ClevoOpenBoardPkg/N1xxWU: Flash map update

Updates the total BIOS flash image size to 0x5E0000. This size
matches the BIOS region size already configured in the SPI
flash descriptor.

To write an image produced from the N1xxWU board build, write
the N1XXWU.fd file (~6 MB) to the beginning of the BIOS region
in the SPI flash (currently 0x220000).

Always back up the original SPI flash image. These offsets and
sizes are subject to change over time.

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>