build fails due to dhcpcd for arm

[Rin Okuyama <rokuyama%rk.phys.keio.ac.jp@localhost>]

Hi,

I observed build failure due to new dhcpcd for evbearmv7hf-eb as follows.

/var/build/src/external/bsd/dhcpcd/dist/dhcp.c: In function 'make_message':
/var/build/src/external/bsd/dhcpcd/dist/dhcp.c:893:29: error: conversion to '__uint16_t' from 'int' may alter its value [-Werror=conversion]
    sz = htons((uint16_t)mtu - IP_UDP_SIZE);

Please apply the attached patch below.

Thanks,
Rin
====
--- src/external/bsd/dhcpcd/dist/dhcp.c.orig	2016-05-10 04:23:35.955662782 +0900
+++ src/external/bsd/dhcpcd/dist/dhcp.c	2016-05-10 04:24:17.716271879 +0900
@@ -890,7 +890,7 @@
 			AREA_CHECK(2);
 			*p++ = DHO_MAXMESSAGESIZE;
 			*p++ = 2;
-			sz = htons((uint16_t)mtu - IP_UDP_SIZE);
+			sz = htons((uint16_t)(mtu - IP_UDP_SIZE));
 			memcpy(p, &sz, 2);
 			p += 2;
 		}