ArmPkg/ArmExceptionLib: avoid indirect call if using vector table in place

ArmPkg/ArmExceptionLib: avoid indirect call if using vector table in place

If we are using the vector table in place, there is no need to make an
indirect call to the common handler routine from the vector table entries,
so just use a straight branch instruction in that case.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Reviewed-by: Eugene Cohen <eugene@hp.com>