hw/arm/mps2: Fix ID register errors on AN511 and AN385

hw/arm/mps2: Fix ID register errors on AN511 and AN385

Fix MPS2 SCC config register values for the mps2-an511
and mps2-an385 boards:
 * the SCC_AID bits [23:20] specify the FPGA build target board revision,
   and the SCC_CFG4 register specifies the actual board revision, so
   these should have matching values. Claim to be board revision C,
   consistently -- we had the revision in the wrong part of SCC_AID.
 * SCC_ID bits [15:4] should be the board number in hex, not decimal

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20180823175225.22612-1-peter.maydell@linaro.org