This test was failing for Power 7 due to the lack of hw support
for unaligned accesses.

2018-08-28  Richard Sandiford  <richard.sandiford@arm.com>

gcc/testsuite/
	PR testsuite/87078
	* gcc.dg/vect/slp-37.c: Restrict scan tests to vect_hw_misalign.

From-SVN: r263913