Skip pr80170.c for non-ptr32plus targets

The testcase uses 32 bit or bigger pointer offsets, and
that triggers an ptrofftype_p assert in tree.c.

gcc/testsuite

2017-04-19  Senthil Kumar Selvaraj  <senthil_kumar.selvaraj@atmel.com>

	* gcc.dg/pr80170.c: Require ptr32plus.

From-SVN: r247011