RISC-V: Fix fail of vmv-imm-rv64.c in rv32

RISC-V: Fix fail of vmv-imm-rv64.c in rv32

After update local codebase to the trunk. I realize there is one more
fail in RV32.
After this patch, all fails of RVV are cleaned up.
Thanks.

FAIL: gcc.target/riscv/rvv/autovec/vmv-imm-rv64.c -O3 -ftree-vectorize
(test for excess errors)
Excess errors:
cc1: error: ABI requires '-march=rv32'

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/vmv-imm-rv64.c: Add ABI

Signed-off-by: Juzhe Zhong <juzhe.zhong@rivai.ai>