middle-end: update vector loop upper bounds when early break vect [PR113734]

When doing early break vectorization we should treat the final iteration as
possibly being partial.  This so that when we calculate the vector loop upper
bounds we take into account that final iteration could have done some work.

The attached testcase shows that if we don't then cunroll may unroll the loop an
if the upper bound is wrong we lose a vector iteration.

This is similar to how we adjust the scalar loop bounds for the PEELED case.

gcc/ChangeLog:

	PR tree-optimization/113734
	* tree-vect-loop.cc (vect_transform_loop): Treat the final iteration of
	an early break loop as partial.

gcc/testsuite/ChangeLog:

	PR tree-optimization/113734
	* gcc.dg/vect/vect-early-break_117-pr113734.c: New test.