Add get and set accessors for jtag_speed:

- Setter calls the interface driver callback to improve core encapsulation.
- Use getter in standard JTAG interface drivers and ZY1000 minidriver.


git-svn-id: svn://svn.berlios.de/openocd/trunk@2159 b42882b7-edfa-0310-969c-e2dbd0fdcd60

src/jtag/rlink/rlink.c

@@ -1849,7 +1849,7 @@ int rlink_init(void)
 
 	tap_state_queue_init();
 	dtc_queue_init();
-	rlink_speed(jtag_speed);
+	rlink_speed(jtag_get_speed());
 	rlink_reset(0, 0);
 
 	return ERROR_OK;