ShellPkg/Shell: fix CopyGuid() arg order in EfiShellGetGuidFromName()

ShellPkg/Shell: fix CopyGuid() arg order in EfiShellGetGuidFromName()

The destination GUID comes first; from
"MdePkg/Include/Library/BaseMemoryLib.h":

> GUID *
> EFIAPI
> CopyGuid (
>   OUT GUID       *DestinationGuid,
>   IN CONST GUID  *SourceGuid
>   );

Here "NewGuid" is the GUID looked up by GetGuidFromStringName(), and
"Guid" is where EfiShellGetGuidFromName() has to propagate that result to.

Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Cc: Tim Lewis <tim.lewis@insyde.com>
Reported-by: Tim Lewis <tim.lewis@insyde.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Tim Lewis <tim.lewis@insyde.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>