vgabios: Make sure stdvga_list_modes() doesn't overrun the buffer.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
vgabios: Add option to control use of standard VGA IO ports and ranges.

Add option CONFIG_VGA_STDVGA_PORTS.  When this option is disabled, the
main BIOS code will not attempt to access any of the legacy VGA IO
ports.

Add option CONFIG_VGA_STDVGA_FRAMEBUFFER.  When this option is
disabled, the code to read/write to the 0xA0000-0xC0000 is not
included in the vgabios.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
vgabios: Add support for writing text to framebuffers in high memory.

Add code for manipulating "direct" style linear RGB framebuffers that
may be in high memory.  This adds simple font writing and scrolling
support.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
coreboot: Make coreboot table searching available to other code.

Make the coreboot table searching code available to code outside
coreboot.c, and make it runnable from 16bit mode.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
vgabios: Initial support for coreboot native vga vgabios.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>