MATCH: Avoid recursive zero_one_valued_p for conversions

So when VN finds a name which has a nop conversion, it says
both names are equivalent to each other and the valuaization
function for one will return the other. This normally does not
cause any issues as there is no recursive matches. But after
r14-4038-gb975c0dc3be285, there was one added. So we would
do an infinite recursion on the match and never finish.
This fixes the issue (and adds a comment in match.pd) by
for converts just handle one level instead of being recursive
always.

OK? Bootstrapped and tested on x86_64-linux-gnu with no regressions.

Note the testcase was reduced from tree-ssa-loop-niter.cc and then
changed slightly into C rather than C++ but it still needs exceptions
turned on get the IR that VN would produce this equivalence relationship
going on. Also had to turn off early inline to force put to be inlined later.

	PR tree-optimization/111435

gcc/ChangeLog:

	* match.pd (zero_one_valued_p): Don't do recursion
	on converts.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/compile/pr111435-1.c: New test.