Fix PR 103288, ICE after PHI-OPT, move an assigment when still in use for another bb

Fix PR 103288, ICE after PHI-OPT, move an assigment when still in use for another bb

The problem is r12-5300-gf98f373dd822b35c allows phiopt to recognize more basic blocks
but missed one location where phiopt could move an assignment from the middle block
to the non-middle one.  This patch fixes that.

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

	PR tree-optimization/103288

gcc/ChangeLog:

	* tree-ssa-phiopt.c (value_replacement): Return early if middle
	block has more than one pred.

gcc/testsuite/ChangeLog:

	* gcc.c-torture/compile/pr103288-1.c: New test.