ShellPkg: Update error to be SHELL_STATUS and not EFI_STATUS.


Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Gary Ching-Pang Lin <glin@suse.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>

git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@14475 6f19259b-4bc3-4df7-8a09-765794883524