x86: qemu: Change default vesa mode to 1024x768x32

x86: qemu: Change default vesa mode to 1024x768x32

The default vesa mode was changed since commit 55b4e1b7d999
("x86: Change default FRAMEBUFFER_VESA_MODE of some boards") for
better VxWorks compatibility but with the changes QEMU video console
no longer works. This is because QEMU's vgabios implements the VESA
mode 8:8:8 as 24bpp without an alpha channel, which U-Boot's video
console driver currently does not support yet.

We need change to real 32bpp in order to make it work again. QEMU
vgabios implements the custom 32bpp VESA mode starting from 0x140
(320x200x32) to 0x147 (1600x1200x32). Set it to 0x144 (1024x768x32).

Fixes: 55b4e1b7d999 ("x86: Change default FRAMEBUFFER_VESA_MODE of some boards")
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>