Move Fdt Table Guid from EmbeddedPkg to MdePkg to avoid
unnecessary dependencies on EmbeddedPkg for packages like
ShellPkg. This change may affect modules dependent on
EmbeddedPkg but not on MdePkg, which is unlikely.
Also, per 8c721d6, MdePkg has a more refined implementation
of Fdt as compared to the EmbeddedPkg which was the initial
implementation.
Not moving gFdtVariableGuid since it'll be moved to platform
code.
Continuous-integration-options: PatchCheck.ignore-multi-package
Signed-off-by: Prachotan Bathi <prachotan.bathi@arm.com>