ClevoOpenBoardPkg/N1xxWU: Use shell source directly

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1675



In long term we will remove ShellBinPkg, so now update
platform to use ShellPkg directly.

Cc: Michael Kubacki <michael.a.kubacki@intel.com>
Cc: Ankit Sinha <ankit.sinha@intel.com>
Cc: Nate DeSimone <nathaniel.l.desimone@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Michael Kubacki <michael.a.kubacki@intel.com>
Reviewed-by: Nate DeSimone <nathaniel.l.desimone@intel.com>
Reviewed-by: Ankit Sinha <ankit.sinha@intel.com>