targets/pipe-loader: drop driver_descriptor symbol from swrast

The symbol is used for hardware only drivers. For swrast the
loader uses swrast_create_screen. Add VISIBILITY_CFLAGS while
we're here.

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>

src/gallium/targets/pipe-loader/Makefile.am

@@ -27,7 +27,8 @@ AM_CPPFLAGS = \
 	-I$(top_srcdir)/include \
 	-I$(top_srcdir)/src/gallium/drivers \
 	-I$(top_srcdir)/src/gallium/winsys \
-	 $(LIBDRM_CFLAGS) \
+	$(LIBDRM_CFLAGS) \
+	$(VISIBILITY_CFLAGS) \
 	-DGALLIUM_RBUG \
 	-DGALLIUM_TRACE \
 	-DGALLIUM_GALAHAD

src/gallium/targets/pipe-loader/pipe_swrast.c

@@ -6,9 +6,6 @@
 PUBLIC struct pipe_screen *
 swrast_create_screen(struct sw_winsys *ws);
 
-PUBLIC
-DRM_DRIVER_DESCRIPTOR("swrast", NULL, NULL, NULL)
-
 struct pipe_screen *
 swrast_create_screen(struct sw_winsys *ws)
 {