EmbeddedPkg/FdtPlatformDxe: Run FDT installation process at TPL_APPLICATION level

EmbeddedPkg/FdtPlatformDxe: Run FDT installation process at TPL_APPLICATION level

The current mechanism relies on EndOfDxe event that runs at TPL_CALLBACK level.
It prevents some protocols to run as excepted because they require TPL_CALLBACK
(eg: TFTP transfer).

This change moves FDT installation in the driver entrypoint (that is called at
TPL_APPLICATION level).

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Olivier Martin <olivier.martin@arm.com>
Reviewed-by: Ronald Cron <Ronald.Cron@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17298 6f19259b-4bc3-4df7-8a09-765794883524