Define a new board model for the MPS2 with an AN505 FPGA image
containing a Cortex-M33. Since the FPGA images for TrustZone
cores (AN505, and the similar AN519 for Cortex-M23) have a
significantly different layout of devices to the non-TrustZone
images, we use a new source file rather than shoehorning them
into the existing mps2.c.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180220180325.29818-20-peter.maydell@linaro.org