EmbeddedPkg: do not ASSERT() on valid external input

EmbeddedPkg: do not ASSERT() on valid external input

Since ASSERT()s are enabled even on all ArmPlatformPkg RELEASE
builds, ASSERT()ing on a valid FDT header will crash the firmware
if the user selects an incorrect file. Since ASSERT() is meant to
catch internal inconsistencies in the firmware, its use here is
inappropriate.

Instead, handle it as a normal error condition.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Olivier Martin <olivier.martin@arm.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@17309 6f19259b-4bc3-4df7-8a09-765794883524