iris: Return non-zero stride for clear color plane
Before this patch, when querying the clear color plane's stride, iris would return the aux surface stride. This was okay because the clear color plane wasn't really used for anything. This doesn't work on XeHP however. On that platform, the aux surface stride is zero (because it doesn't have an ISL surface for the CCS). This is a problem because mesa's implementation of eglCreateImage rejects strides of zero (see dri2_check_dma_buf_attribs) and this value may be queried from GBM and passed into EGL. When the DG2 clear color modifier is enabled, this avoids EGL_BAD_ACCESS errors when running the piglit test, ext_image_dma_buf_import-intel_modifiers. Reviewed-by:Tapani Pälli <tapani.palli@intel.com> Part-of: <mesa/mesa!14759>