freedreno: Enable texture upload memory throttling.

Fixes oom-killer during streaming-texture-upload, which I found while
trying to enable piglit in CI.

Reviewed-by: Rob Clark <robdclark@chromium.org>

src/gallium/drivers/freedreno/freedreno_screen.c

@@ -353,6 +353,9 @@ fd_screen_get_param(struct pipe_screen *pscreen, enum pipe_cap param)
 		 */
 		return 128;
 
+	case PIPE_CAP_MAX_TEXTURE_UPLOAD_MEMORY_BUDGET:
+		return 64 * 1024 * 1024;
+
 	case PIPE_CAP_SHAREABLE_SHADERS:
 	case PIPE_CAP_GLSL_OPTIMIZE_CONSERVATIVELY:
 	/* manage the variants for these ourself, to avoid breaking precompile: */