[committed][RISC-V] Fix test expectations after recent late-combine changes

With the recent DCE related adjustment to late-combine the rvv/base/vcreate.c
test no longer has those undesirable vmvNr statements.

It's a bit unclear why this wasn't written as a scan-assembler-not and xfailed
given the comment says we don't want to see vmvNr insructions.  I must have
missed that during review.

This patch adjusts the test to expect no vmvNr statements and if they're ever
re-introduced, we'll get a nice unexpected failure.

gcc/testsuite
	* gcc.target/riscv/rvv/base/vcreate.c: Update expected output.