hw/arm/xilinx_zynq: Include missing 'exec/tswap.h' header

hw/arm/xilinx_zynq: Include missing 'exec/tswap.h' header

hw/arm/xilinx_zynq.c calls tswap32() which is declared
in "exec/tswap.h". Include it in order to avoid when
refactoring unrelated headers:

  hw/arm/xilinx_zynq.c:103:31: error: call to undeclared function 'tswap32';
  ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
          board_setup_blob[n] = tswap32(board_setup_blob[n]);
                                ^

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20240118200643.29037-3-philmd@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>