The dhcp-3.0-4.i386.rpm package contains devel files which are not necessary for
"normal" usage and the dhcrelay program which has other purposes than dhcpd and
conflicts with it.

To make lightweighted installations possible I suggest to add dhcp-devel and
dhcrelay subpackages; appropriate %files sections could look like

----
%files devel
%defattr(-,root,root)
/usr/include/*
%{_libdir}/*.a
%{_mandir}/man3/*

%files -n dhcrelay
%defattr(-,root,root)
%config(noreplace) /etc/sysconfig/dhcrelay
%config /etc/rc.d/init.d/dhcrelay
%{_sbindir}/dhcrelay
%{_mandir}/man8/dhcrelay.8*