crc: Error out on non-constant poly arguments for the crc builtins [PR120709]

crc: Error out on non-constant poly arguments for the crc builtins [PR120709]

These builtins requires a constant integer for the third argument but currently
there is assert rather than error. This fixes that and updates the documentation too.
Uses the same terms as was being used for the __builtin_prefetch arguments.

Bootstrapped and tested on x86_64-linux-gnu.

	PR middle-end/120709

gcc/ChangeLog:

	* builtins.cc (expand_builtin_crc_table_based): Error out
	instead of asserting the 3rd argument is an integer constant.
	* internal-fn.cc (expand_crc_optab_fn): Likewise.
	* doc/extend.texi (crc): Document requirement of the poly argument
	being a constant.

gcc/testsuite/ChangeLog:

	* gcc.dg/crc-non-cst-poly-1.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>