[pcap] Write incoming packages without the extra mISDN header

This patch fixes the PCAP logging. If frames are received from E1
interface, an 8 byte mISDN header (MISDN_HEADER_LEN) is in front of the
RSL packet. When frames are transmitted to the E1 interface, the
pcap_write_packet function will get a message buffer without the mISDN
header in front of the RSL packet. The pcap file was tested and the
output is correct.

Follow up patches should make use the msgb->l2, make the ipaccess
code use the pcap writing too...
diff --git a/openbsc/src/e1_input.c b/openbsc/src/e1_input.c
index c3c7c75..034bd97 100644
--- a/openbsc/src/e1_input.c
+++ b/openbsc/src/e1_input.c
@@ -140,6 +140,7 @@
 	int ret;
 	time_t cur_time;
 	struct tm *tm;
+	int mi_head = (direction==PCAP_INPUT) ? MISDN_HEADER_LEN : 0;
 
 	struct fake_linux_lapd_header header = {
 		.pkttype	= 4,
@@ -163,13 +164,15 @@
 		.ts_usec    = 0,
 		.incl_len   = msg->len + sizeof(struct fake_linux_lapd_header)
 				+ sizeof(struct lapd_header)
-				- MISDN_HEADER_LEN,
+				- mi_head,
 		.orig_len   = msg->len + sizeof(struct fake_linux_lapd_header)
 				+ sizeof(struct lapd_header)
-				- MISDN_HEADER_LEN,
+				- mi_head,
 	};
 
 
+        printf("Packet of: %d\n", direction);
+
 	cur_time = time(NULL);
 	tm = localtime(&cur_time);
 	payload_header.ts_sec = mktime(tm);
@@ -177,8 +180,8 @@
 	ret = write(pcap_fd, &payload_header, sizeof(payload_header));
 	ret = write(pcap_fd, &header, sizeof(header));
 	ret = write(pcap_fd, &lapd_header, sizeof(lapd_header));
-	ret = write(pcap_fd, msg->data + MISDN_HEADER_LEN,
-			msg->len - MISDN_HEADER_LEN);
+	ret = write(pcap_fd, msg->data + mi_head,
+			msg->len - mi_head);
 }
 
 static const char *sign_types[] = {