[InstCombine] ease use constraint in tryFactorization()

The stronger one-use checks prevented transforms like this:
(x * y) + x --> x * (y + 1)
(x * y) - x --> x * (y - 1)

https://alive2.llvm.org/ce/z/eMhvQa

This is one of the IR transforms suggested in issue #57255.

This should be better in IR because it removes a use of a
variable operand (we already fold the case with a constant
multiply operand).
The backend should be able to re-distribute the multiply if
that's better for the target.

Differential Revision: https://reviews.llvm.org/D132412