xlnx_dp: fix the wrong register size

xlnx_dp: fix the wrong register size

The core and the vblend registers size are wrong, they should respectively be
0x3B0 and 0x1E0 according to:
  https://www.xilinx.com/htmldocs/registers/ug1087/ug1087-zynq-ultrascale-registers.html.

Let's fix that and use macros when creating the mmio region.

Fixes: 58ac482a66d ("introduce xlnx-dp")
Signed-off-by: Frederic Konrad <fkonrad@amd.com>
Reviewed-by: Edgar E. Iglesias <edgar.iglesias@amd.com>
Acked-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20220601172353.3220232-2-fkonrad@xilinx.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>