x86: replace EXqScalarS by EXqVexScalarS

x86: replace EXqScalarS by EXqVexScalarS

There's only a single user, that that one can do fine with the
alternative, as the "Vex" aspect of the other operand kind is meaningful
only on 3-operand insns.

While doing this I noticed that I didn't need to do the same adjustment
in the EVEX tables, and voilà - there was a bug, which gets fixed at the
same time (see the testsuite changes).