hw/arm/digic4: Inline digic4_board_setup_ram() function

hw/arm/digic4: Inline digic4_board_setup_ram() function

Having the RAM creation code in a separate function is not
very helpful. Move this code directly inside the board_init()
function, this will later allow the board to have the QOM
ownership of the RAM.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-id: 20191021190653.9511-7-philmd@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>