EmbeddedPkg/FdtPlatformDxe: Do not exit if RunFdtInstallation() fails

EmbeddedPkg/FdtPlatformDxe: Do not exit if RunFdtInstallation() fails

If the device trees are not present when loading FdtPLatformDxe
driver then we should prevent to install the EFI Shell FDT commands.

The EFI Shell commands could be used later to install the missing
device tree.

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@17441 6f19259b-4bc3-4df7-8a09-765794883524