Fix missing _SEW_ in vmax_vx

There was a similar error from a newer test, prompting re-evaluation
of the test it was based on.

Macro was missing _SEW_, and was only working for vle8, but this still
passed the tests, so looking closer filled in the section that was
present in the demo test, but missing in the macro.

Change-Id: I50b4ab206f936f4a1c11d201f19edcb8f830744d
1 file changed