tree-ssa-mathopts: Use proper poly_int64 comparison with param_avoid_fma_max_bits...

tree-ssa-mathopts: Use proper poly_int64 comparison with param_avoid_fma_max_bits [PR 98766]

We ICE here because we end up comparing a poly_int64 with a scalar using
<= rather than maybe_le.
This patch fixes that in the way rich suggests in the PR.

gcc/ChangeLog:

	PR tree-optimization/98766
	* tree-ssa-math-opts.c (convert_mult_to_fma): Use maybe_le when
	comparing against type size with param_avoid_fma_max_bits.

gcc/testsuite/ChangeLog:

	PR tree-optimization/98766
	* gcc.dg/pr98766.c: New test.

(cherry picked from commit 9d33785f57daf29dc0c106c919da319fe1906bc6)