arm: add Cortex A7 CPU parameters

Add the "cortex-a7" CPU with features and registers matching the Cortex-A7
MPCore Technical Reference Manual and the Cortex-A7 Floating-Point Unit
Technical Reference Manual. The A7 is very similar to the A15.

Signed-off-by: Andrey Yurovsky <yurovsky@gmail.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1473185229-4597-1-git-send-email-yurovsky@gmail.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>