Adds a dedicated function and a lookup table for determining the target
exception level of IRQ and FIQ exceptions.  The lookup table is taken from the
ARMv7 and ARMv8 specification exception routing tables.
Signed-off-by: NGreg Bellows <greg.bellows@linaro.org>
Reviewed-by: NPeter Maydell <peter.maydell@linaro.org>
Message-id: 1416242878-876-3-git-send-email-greg.bellows@linaro.org
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>