net: convert NET_MAXDEFRAG to Kconfig

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/net/Kconfig b/net/Kconfig
index a07f674..96bbce1 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -29,6 +29,16 @@
 	  Selecting this will enable IP datagram reassembly according
 	  to the algorithm in RFC815.
 
+config NET_MAXDEFRAG
+	int "Size of buffer used for IP datagram reassembly"
+	depends on IP_DEFRAG
+	default 16384
+	range 1024 65536
+	help
+	  This defines the size of the statically allocated buffer
+	  used for reassembly, and thus an upper bound for the size of
+	  IP datagrams that can be received.
+
 config TFTP_BLOCKSIZE
 	int "TFTP block size"
 	default 1468