net-caif-driver: add CAIF serial driver (ldisc)

Add CAIF Serial driver. This driver is implemented as a line discipline.

caif_serial uses the following module parameters:
ser_use_stx - specifies if STart of frame eXtension is in use.
ser_loop    - sets the interface in loopback mode.

Signed-off-by: Sjur Braendeland <sjur.brandeland@stericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 568369a..71c7e9c 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -23,7 +23,7 @@
  */
 #define NR_UNIX98_PTY_DEFAULT	4096      /* Default maximum for Unix98 ptys */
 #define NR_UNIX98_PTY_MAX	(1 << MINORBITS) /* Absolute limit */
-#define NR_LDISCS		20
+#define NR_LDISCS		21
 
 /* line disciplines */
 #define N_TTY		0
@@ -46,8 +46,8 @@
 #define N_GIGASET_M101	16	/* Siemens Gigaset M101 serial DECT adapter */
 #define N_SLCAN		17	/* Serial / USB serial CAN Adaptors */
 #define N_PPS		18	/* Pulse per Second */
-
 #define N_V253		19	/* Codec control over voice modem */
+#define N_CAIF		20      /* CAIF protocol for talking to modems */
 
 /*
  * This character is the same as _POSIX_VDISABLE: it cannot be used as