[OpenBIOS] Sparc64 alignment fix

[Blue Swirl]

Hi,

Currently Qemu does not enforce correct alignment on Sparc32/64
targets, but a patch by Aurelien Jarno would change that to match the
real life CPUs.

But before the patch can get in, problems with unaligned memory
accesses in OpenBIOS must be corrected. This patch fixes the stack
alignment problem on Sparc64 (actually caused by gcc, see gcc
-mstack-bias).