x86: templatize shift-double insns

With the multitude of new APX templates, it finally becomes desirable to
further remove redundancy by also templatizing basic arithmetic insns.
Continue with the shift-double ones.

While there also drop the APX form with ShiftCount omitted. Other shift
and rotate insns were deliberately left without this form as well. Note
that there's also no testsuite adjustment needed for this, indicating
that the form wasn't tested either.