match: Fix incorrect identification of POPCOUNT pattern [PR126466]

This fixes r17-489-g8ca1e887847e2f, which added a third 32-bit
Hacker's Delight popcount matcher.  Its predicate checked
compare_tree_int (@5, 0x0F0F0F0F) twice and never validated the
final outer AND constant (@7), so any mask was accepted once the
earlier constants matched.

Require compare_tree_int (@7, 0x0000003F) so only the intended
popcount idiom is folded to IFN_POPCOUNT.

gcc/ChangeLog:

	PR tree-optimization/126466
	* match.pd: Fix incorrect POPCOUNT identification in the third
	32-bit Hacker's Delight matcher.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/popcount10.c: New test.