ArmPlatformPkg: Fix Ecc error 10016 in LcdPlatformNullLib

ArmPlatformPkg: Fix Ecc error 10016 in LcdPlatformNullLib

This patch fixes the following Ecc reported error:
Module file has FILE_GUID collision with other
module file

The two .inf files with clashing GUID are:
edk2\ArmPlatformPkg\PrePeiCore\PrePeiCoreMPCore.inf
edk2\ArmPlatformPkg\Library\LcdPlatformNullLib\LcdPlatformNullLib.inf

The PrePeiCoreMPCore module has been imported in 2011 and the
LcdPlatformNullLib module has been created in 2017. The
PrePeiCoreMPCore has the precedence.

Signed-off-by: Pierre Gondois <Pierre.Gondois@arm.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@arm.com>