ENTER/BOUND operands order.

[Michael Zolotukhin]

This document "syntax" is not the actual assembly syntax.  The
presence of {er} or {sae} there just means the instruction supports
those encodings.  I agree that it could lead to some confusion, but
this document describes instructions, not syntax.

Unfortunately, there is no document describing the assembly syntax (at
least, to my knowledge), and the tests are the best reference point we
have.

Thanks,
Michael