Use signed loop iteration variable in nvtpx/slp* test-cases to work around
PR tree-optimizaion/81635.

2017-08-01  Tom de Vries  <tom@codesourcery.com>

	* gcc.target/nvptx/slp-2.c (foo): Use signed loop iteration variable.
	* gcc.target/nvptx/slp.c (foo): Same.

From-SVN: r250778