get roms more room. (Glauber Costa)

get roms more room. (Glauber Costa)

This patch increases by 50 % the size available for option roms.
The main motivator is that some roms grew bigger than the 64k we
currently allocate for them (Hey, it's 2009!)

One example is the gpxe project, that produces some roms with 69k,
70k, etc. The space proposed by this patch actually makes it as
big as 84k. Probably still a fit for some time.

But there is no free lunch. This space must come from somewhere,
and we take it from vga rom space. Currently, our vga roms are
around 35k in size. With this patch, option rom space will begin
just after vga ends, aligned to the next 2k boundary.

Technicaly, we could do the same with the uper space (the bios itself),
but since bochs bios is already 128 k in size, I don't see an
urgent need to do it.

[ fix case for vgabioses smaller than 30k, by Carl-Daniel Hailfinger ]

Signed-off-by: Glauber Costa <glommer@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@6896 c046a42c-6fe2-441c-8c8c-71466251a162