ArmPkg/DefaultExceptionHandlerLib: use console if available

ArmPkg/DefaultExceptionHandlerLib: use console if available

Print the minimal 'exception occurred' message to the console as well
as to the serial port if the console is available. This makes such
messages visible on systems where the console is graphical and the
serial is not connected.

Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Reviewed-by: Leif Lindholm <leif.lindholm@linaro.org>
Acked-by: Laszlo Ersek <lersek@redhat.com>