RISC-V: Bugfix for allowing incorrect dyn for static rounding

RISC-V: Bugfix for allowing incorrect dyn for static rounding

According to the spec, dyn rounding mode is invalid for RVV
floating-point, this patch would like to fix this.

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

	* config/riscv/riscv-vector-builtins-shapes.cc
	(struct alu_frm_def): Take range check.

gcc/testsuite/ChangeLog:

	* gcc.target/riscv/rvv/base/float-point-frm-error.c: Update cases.
	* gcc.target/riscv/rvv/base/float-point-frm-insert-6.c: Removed.