udhcpd: don't fail ARP check if returned MAC matches client's one

Also, do not unicast replies to yiaddr.

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/networking/udhcp/dhcpd.h b/networking/udhcp/dhcpd.h
index 9667c61..4b5fcc0 100644
--- a/networking/udhcp/dhcpd.h
+++ b/networking/udhcp/dhcpd.h
@@ -99,7 +99,7 @@
 int lease_expired(struct dhcpOfferedAddr *lease) FAST_FUNC;
 struct dhcpOfferedAddr *find_lease_by_chaddr(const uint8_t *chaddr) FAST_FUNC;
 struct dhcpOfferedAddr *find_lease_by_yiaddr(uint32_t yiaddr) FAST_FUNC;
-uint32_t find_free_or_expired_address(void) FAST_FUNC;
+uint32_t find_free_or_expired_address(const uint8_t *chaddr) FAST_FUNC;
 
 
 /*** static_leases.h ***/