test: Fix FAIL of bb-slp-cond-1.c for RVV

test: Fix FAIL of bb-slp-cond-1.c for RVV

This patch fixes:
FAIL: gcc.dg/vect/bb-slp-cond-1.c -flto -ffat-lto-objects  scan-tree-dump-times vect "loop vectorized" 1
FAIL: gcc.dg/vect/bb-slp-cond-1.c scan-tree-dump-times vect "loop vectorized" 1

For RVV, "loop vectorized" appears 2 times instead of 1. Because:
optimized: loop vectorized using 16 byte vectors
optimized: loop vectorized using 8 byte vectors

As long as targets have both 64bit and 128bit vectors, it will occur 2 times.
2 targets are same situation, one is AMDGCN, the other is RVV.

Replace it target amdgcn with vect64 && vect128 to make test more general and easy maintain.

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/bb-slp-cond-1.c: Fix FAIL.