r300g: Use u_trim_pipe_prim to prevent lockups from incorrect vert counts.

Adapted from osiris' version on his tree.

src/gallium/drivers/r300/r300_render.c

@@ -26,6 +26,7 @@
 #include "pipe/p_inlines.h"
 
 #include "util/u_memory.h"
+#include "util/u_prim.h"
 
 #include "r300_cs.h"
 #include "r300_context.h"
@@ -86,6 +87,10 @@ boolean r300_draw_range_elements(struct pipe_context* pipe,
     
     CS_LOCALS(r300);
 
+    if (!u_trim_pipe_prim(mode, &count)) {
+        return FALSE;
+    }
+
 validate:
     for (i = 0; i < aos_count; i++) {
         if (!r300->winsys->add_buffer(r300->winsys, aos[i].buffer,
@@ -191,6 +196,10 @@ boolean r300_swtcl_draw_range_elements(struct pipe_context* pipe,
     struct r300_context* r300 = r300_context(pipe);
     int i;
 
+    if (!u_trim_pipe_prim(mode, &count)) {
+        return FALSE;
+    }
+
     for (i = 0; i < r300->vertex_buffer_count; i++) {
         void* buf = pipe_buffer_map(pipe->screen,
                                     r300->vertex_buffers[i].buffer,