[nvptx] Eliminate changed local var in nvptx_goacc_validate_dims

[nvptx] Eliminate changed local var in nvptx_goacc_validate_dims

The TARGET_GOACC_VALIDATE_DIMS hook requires an implementation to return a bool
indicating whether the dims parameter has changed.

Factor nvptx_goacc_validate_dims_1 out of nvptx_goacc_validate_dims, and
calculate the return value in nvptx_goacc_validate_dims.

2019-01-03  Tom de Vries  <tdevries@suse.de>

	* config/nvptx/nvptx.c (nvptx_goacc_validate_dims_1): New function,
	factored out of ...
	(nvptx_goacc_validate_dims): ... here.

From-SVN: r267555