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/presto.c

@@ -787,7 +787,7 @@ static int presto_jtag_init(void)
 	LOG_INFO("PRESTO open, serial number '%s'", presto->serial);
 
 	/* use JTAG speed setting from configuration file */
-	presto_jtag_speed(jtag_speed);
+	presto_jtag_speed(jtag_get_speed());
 
 	bitq_interface = &presto_bitq;
 	return ERROR_OK;