When CPU vendor is set to AMD, the AMD feature alias bits on
CPUID[0x80000001].EDX are already automatically copied from CPUID[1].EDX
on x86_cpu_realizefn(). When CPU vendor is Intel, those bits are
reserved and should be zero. On either case, those bits shouldn't be set
in the CPU model table.
Commit 726a8ff68677d8d5fba17eb0ffb85076bfb598dc removed those
bits from most CPU models, but the Opteron_* entries still have
them. Remove the alias bits from Opteron_* too.
Add an assert() to x86_register_cpudef_type() to ensure we don't
make the same mistake again.
Backports commit 2a923a293df95334fa22634016efdd138f49da7f from qemu
f424e16f24