CDP: Remove a useless line

The value was fetched before:
	al = EXTRACT_16BITS(&p[pl]);    /* address length */
diff --git a/print-cdp.c b/print-cdp.c
index 6f8f356..311f2c2 100644
--- a/print-cdp.c
+++ b/print-cdp.c
@@ -347,7 +347,6 @@
 			ND_TCHECK2(*p, 2);
 			if (p + 2 > endp)
 				goto trunc;
-			al = (*p << 8) + *(p + 1);
 			ND_PRINT((ndo, ", al=%d, a=", al));
 			p += 2;
 			ND_TCHECK2(*p, al);