arm: qemu: Enable PRE_CONSOLE_BUFFER

Commit 608b80b5 ("riscv: qemu: Enable PRE_CONSOLE_BUFFER") enables
buffering console messages for QEMU RISC-V virtual machines so those
printed before the video console is available will still show up on the
display. Similarly, enable it for ARM virtual machines as well.

Signed-off-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng@tinylab.org>