EmbeddedPkg: Split off FDT loading functionality from FdtLib

EmbeddedPkg: Split off FDT loading functionality from FdtLib

Split off the recently added functionality to load device tree images and
install them as configuration tables, as it introduces a dependency on
UefiBootServicesTableLib, preventing FdtLib from being used during SEC and
PEI phases.

Contributed-under: TianoCore Contribution Agreement 1.0
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Olivier Martin <olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@16080 6f19259b-4bc3-4df7-8a09-765794883524