[testsuite] Fix PR94019 to check vector char when vect_hw_misalign

[testsuite] Fix PR94019 to check vector char when vect_hw_misalign

As PR94019 shows, without misaligned vector access support but with
realign load, the vectorized loop will end up with realign scheme.
It generates mask (control vector) with return type vector signed
char which breaks the not check.

gcc/testsuite/ChangeLog

2020-03-09  Kewen Lin  <linkw@gcc.gnu.org>

    PR testsuite/94019
    * gcc.dg/vect/vect-over-widen-17.c: Don't expect vector char if
    it's without misaligned vector access support.