rs6000: Shut up -Wformat-diag a little more

rs6000: Shut up -Wformat-diag a little more

	PR target/91148
	* config/rs6000/rs6000-c.c (altivec_resolve_overloaded_builtin): Remove
	superfluous "builtin function" phrasing.

gcc/testsuite/
	* gcc.target/powerpc/bfp/scalar-extract-exp-2.c: Adjust.
	* gcc.target/powerpc/bfp/scalar-extract-sig-2.c: Adjust.
	* gcc.target/powerpc/bfp/scalar-insert-exp-2.c: Adjust.
	* gcc.target/powerpc/bfp/scalar-insert-exp-5.c: Adjust.
	* gcc.target/powerpc/bfp/scalar-insert-exp-8.c: Adjust.
	* gcc.target/powerpc/byte-in-set-2.c: Adjust.
	* gcc.target/powerpc/cmpb-3.c: Adjust.
	* gcc.target/powerpc/vsu/vec-all-nez-7.c: Adjust.
	* gcc.target/powerpc/vsu/vec-any-eqz-7.c: Adjust.
	* gcc.target/powerpc/vsu/vec-xl-len-13.c: Adjust.
	* gcc.target/powerpc/vsu/vec-xst-len-12.c: Adjust.

From-SVN: r273475