jtag interfaces: Reduce usage of global for jtag queue

Makes driver interface slightly more flexible.

Change-Id: I2c7f5cb6d014e94a0e6122cbe2f4002c77fbabb9
Signed-off-by: Evan Hunter <ehunter@broadcom.com>
Signed-off-by: David Ryskalczyk <david.rysk@gmail.com>
Reviewed-on: https://review.openocd.org/c/openocd/+/945
Reviewed-by: Antonio Borneo <borneo.antonio@gmail.com>
Tested-by: jenkins

src/jtag/interface.h

@@ -187,10 +187,12 @@ struct jtag_interface {
 #define DEBUG_CAP_TMS_SEQ	(1 << 0)
 
 	/**
-	 * Execute queued commands.
+	 * Execute commands in the supplied queue
+	 * @param cmd_queue - a linked list of commands to execute
 	 * @returns ERROR_OK on success, or an error code on failure.
 	 */
-	int (*execute_queue)(void);
+
+	int (*execute_queue)(struct jtag_command *cmd_queue);
 };
 
 /**