Minor - move PORT_PS2_CTRLB from hw/ps2port.h to hw/timer.c

The PORT_PS2_CTRLB port is only used by timers - it's just a
historical artifact that it was part of the original ps2 controller.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
vgabios: Support emulating text mode attributes while in graphics mode

Add support for simple text mode attribute emulation while in graphics
mode.  This improves text highlighting and background color on some
boot-loaders.  Enable it only for CBVGA vgabios and only when a text
mode is requested.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
vgabios: Add software cursor capability

Add mechanism for drawing a cursor to the framebuffer to implement a
cursor in software.  The timer interrupt is "hooked" so that the
cursor can blink.  This can be useful for "coreboot native vga".

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
Use an aligned stack offset when entering on the extra stack

The size of 'struct bregs' is not evenly divisible by four and where
the assembler placed a 'struct bregs' on the extra stack as part of
entering into the C functions it caused the C functions to run with a
non-aligned stack.  It's technically not correct to use an unaligned
stack and it is certainly less efficient.

This patch avoids using BREGS_size (the sizeof struct bregs) and
instead introduces PUSHBREGS_size (the size of the general purpose
registers in struct bregs) in the assembler.  Where the code actually
did use the %cs:%ip and flags, an extra 8 (instead of 6) bytes are
added to maintain a sane alignment.

Signed-off-by: Kevin O'Connor <kevin@koconnor.net>
Minor - comment updates in romlayout.S

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