caif: Use link layer MTU instead of fixed MTU

Previously CAIF supported maximum transfer size of ~4050.
The transfer size is now calculated dynamically based on the
link layers mtu size.

Signed-off-by: Sjur Braendeland@stericsson.com
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/caif/cfpkt_skbuff.c b/net/caif/cfpkt_skbuff.c
index 318b0f4..01f238f 100644
--- a/net/caif/cfpkt_skbuff.c
+++ b/net/caif/cfpkt_skbuff.c
@@ -9,8 +9,8 @@
 #include <linux/hardirq.h>
 #include <net/caif/cfpkt.h>
 
-#define PKT_PREFIX CAIF_NEEDED_HEADROOM
-#define PKT_POSTFIX CAIF_NEEDED_TAILROOM
+#define PKT_PREFIX  16
+#define PKT_POSTFIX 2
 #define PKT_LEN_WHEN_EXTENDING 128
 #define PKT_ERROR(pkt, errmsg) do {	   \
     cfpkt_priv(pkt)->erronous = true;	   \