gallium/util: another unsigned -> enum pipe_prim_type change

gcc didn't warn about the unsigned / enum pipe_prim_type mismatch
between the .c and .h file.

Reviewed-by: Roland Scheidegger <sroland@vmware.com>

src/gallium/auxiliary/util/u_debug.c

@@ -423,7 +423,7 @@ debug_print_format(const char *msg, unsigned fmt )
 
 /** Return string name of given primitive type */
 const char *
-u_prim_name(unsigned prim)
+u_prim_name(enum pipe_prim_type prim)
 {
    static const struct debug_named_value names[] = {
       DEBUG_NAMED_VALUE(PIPE_PRIM_POINTS),