Revert "n_gsm.c: add tx_lock in gsm_send"

This reverts commit f96f7f7f39af53274d98aa9c29d6fa4d122218a4, at the
request of Jin.

Cc: xiaojin <jin.xiao@intel.com>
Cc: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/n_gsm.c

@@ -573,7 +573,6 @@ static void gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
 	int len;
 	u8 cbuf[10];
 	u8 ibuf[3];
-	unsigned long flags;
 
 	switch (gsm->encoding) {
 	case 0:
@@ -603,9 +602,7 @@ static void gsm_send(struct gsm_mux *gsm, int addr, int cr, int control)
 		WARN_ON(1);
 		return;
 	}
-	spin_lock_irqsave(&gsm->tx_lock, flags);
 	gsm->output(gsm, cbuf, len);
-	spin_unlock_irqrestore(&gsm->tx_lock, flags);
 	gsm_print_packet("-->", addr, cr, control, NULL, 0);
 }