Fix typo in net/dhcpcd README

Hi,

The diff below fixes a typo in the README: no underscore between
"rtadvd" and "flags".

Thanks,
Caspar Schutijser


Index: Makefile
===================================================================
RCS file: /cvs/ports/net/dhcpcd/Makefile,v
retrieving revision 1.25
diff -u -p -r1.25 Makefile
--- Makefile 13 Sep 2017 11:03:51 -0000 1.25
+++ Makefile 13 Sep 2017 19:44:13 -0000
@@ -3,7 +3,7 @@
COMMENT= DHCPv4/IPv4LL/IPv6RS/DHCPv6 quad stack client

DISTNAME= dhcpcd-6.11.5
-REVISION= 3
+REVISION= 4

CATEGORIES= net
EXTRACT_SUFX= .tar.xz
Index: pkg/README
===================================================================
RCS file: /cvs/ports/net/dhcpcd/pkg/README,v
retrieving revision 1.3
diff -u -p -r1.3 README
--- pkg/README 13 Sep 2017 11:03:51 -0000 1.3
+++ pkg/README 13 Sep 2017 19:44:13 -0000
@@ -37,4 +37,4 @@ interface pppoe0
-- -- -- -- -- --

In normal cases, you would use rtadvd(8) to advertise these prefixes to
-clients (e.g. "rcctl enable rtadvd; rcctl set rtadvd_flags em0 vlan3 vlan5").
+clients (e.g. "rcctl enable rtadvd; rcctl set rtadvd flags em0 vlan3 vlan5").