bios_emulator: Drop VIDEO_IO_OFFSET

This is always zero in the source tree, so drop it.

While we are here, add a comment to _X86EMU_env since the symbol is
actually defined twice, which can cause confusion when building.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
8 files changed