RISC-V: Fix V_WHOLE && V_FRACT iterator requirement

This patch fixes the requirement of V_WHOLE and V_FRACT.
E.g. VNx8QI in V_WHOLE has no requirement which is incorrect.
     Actually, VNx8QI should be whole(full) mode when TARGET_MIN_VLEN < 128
     since when TARGET_MIN_VLEN == 128, VNx8QI is e8mf2 which is fractional
     vector.

Co-Authored by: Robin Dapp <rdapp@ventanamicro.com>

gcc/ChangeLog:

	* config/riscv/vector-iterators.md: Fix requirement.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/autovec/vls-vlmax/full-vec-move1.c: New test.