tools: selftests: riscv: Add pass message for v_initval_nolibc

Add the pass message after we successfully complete the test.

Fixes: 5c93c4c7 ("selftests: Test RISC-V Vector's first-use handler")
Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Reviewed-by: Andy Chiu <AndybnAC@gmail.com>
Link: https://lore.kernel.org/r/20241220091730.28006-2-yongxuan.wang@sifive.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>