RISC-V Regression: Fix FAIL of bb-slp-pr65935.c for RVV

Here is the reference comparing dump IR between ARM SVE and RVV.

https://godbolt.org/z/zqess8Gss

We can see RVV has one more dump IR:
optimized: basic block part vectorized using 128 byte vectors
since RVV has 1024 bit vectors.

The codegen is reasonable good.

However, I saw GCN also has 1024 bit vector.
This patch may cause this case FAIL in GCN port ?

Hi, GCN folk, could you check this patch in GCN port for me ?

gcc/testsuite/ChangeLog:

	* gcc.dg/vect/bb-slp-pr65935.c: Add vect1024 variant.
	* lib/target-supports.exp: Ditto.