9233989: ecx and edx were mixed up

[Chris Angelico]

For operation 0, the text string is indeed returned in
[EAX]/EBX/EDX/ECX. However, the string is used only in src/code/ia32.c
for its detection of AMD vs Intel, so it's entirely possible this
change won't break anything anywhere else. Might merit a comment and
some odd code in that one file, rather than warping other files around
the oddity of that operation. Thoughts?

ChrisA