[testsuite] Fix PR94079 by respecting vect_hw_misalign [PR94079]

[testsuite] Fix PR94079 by respecting vect_hw_misalign [PR94079]

This is another vect case which requires special handling with
vect_hw_misalign.  The alignment of the second part requires
misaligned vector access supports.  This patch is to adjust
the related guard condition and comments.

Verified it on ppc64-redhat-linux (Power7 BE).

2020-04-09  Kewen Lin  <linkw@gcc.gnu.org>

gcc/testsuite/ChangeLog

    PR testsuite/94023
    * gfortran.dg/vect/pr83232.f90: Expect 2 rather than 3 times SLP on
    non-vect_hw_misalign targets.