ArmPkg/DefaultExceptionHandlerLib: put ASSERT (FALSE) last

ArmPkg/DefaultExceptionHandlerLib: put ASSERT (FALSE) last

Putting DEBUG () code after an ASSERT (FALSE) statement is not very
useful, since the code will be unreachable on DEBUG builds and compiled
out on RELEASE builds. So move the ASSERT () statement after it.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Acked-by: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>