RISC-V: Add test for vfloat16*_t (non tuple) types

This patch would like to add some test cases of vfloat16*_t (non tuple),
no 'zvfh' or 'zvfhmin' will meet unknown type.

Signed-off-by: Pan Li <pan2.li@intel.com>

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/abi-16.c: Add test cases.
	* gcc.target/riscv/rvv/base/user-7.c: Likewise.