mISDN: Implement MISDN_CTRL_RX_OFF for more drivers

MISDN_CTRL_RX_OFF is a meachanism to discard RX data in the driver if
the data is not needed by the application. It can be used when playing
mesages, but not recording or with unidirectional protocols.

Signed-off-by: Karsten Keil <kkeil@linux-pingi.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/mISDNhw.h b/include/linux/mISDNhw.h
index 6211842..d0752ec 100644
--- a/include/linux/mISDNhw.h
+++ b/include/linux/mISDNhw.h
@@ -73,6 +73,8 @@
 #define FLG_LL_CONN		25
 #define FLG_DTMFSEND		26
 #define FLG_TX_EMPTY		27
+/* stop sending received data upstream */
+#define FLG_RX_OFF		28
 /* workq events */
 #define FLG_RECVQUEUE		30
 #define	FLG_PHCHANGE		31
@@ -173,6 +175,7 @@
 	int			err_crc;
 	int			err_tx;
 	int			err_rx;
+	int			dropcnt;
 };
 
 extern int	mISDN_initdchannel(struct dchannel *, int, void *);