sys-fabric/rds-tools: port to EAPI 6 (temporarily), drop base.eclass

EAPI 6 for a short period until we update openib.eclass to allow
us to drop base.eclass.

Signed-off-by: Sam James <sam@gentoo.org>

sys-fabric/rds-tools/files/rds-tools-2.0.4-qa.patch

@@ -1,8 +1,8 @@
 Respect CC,CFLAGS, fix install paths, don't strip binaries
 
 https://bugs.gentoo.org/show_bug.cgi?id=374805
---- Makefile.in
-+++ Makefile.in
+--- a/Makefile.in
++++ b/Makefile.in
 @@ -1,12 +1,15 @@
 -prefix		= $(DESTDIR)@prefix@
 -exec_prefix	= $(DESTDIR)@exec_prefix@

sys-fabric/rds-tools/rds-tools-2.0.4-r4.ebuild

@@ -1,23 +1,25 @@
-# Copyright 1999-2018 Gentoo Foundation
+# Copyright 1999-2021 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
-EAPI="5"
+EAPI=6
 
 OFED_VER="3.12"
 OFED_RC="1"
 OFED_RC_VER="1"
 OFED_SUFFIX="1"
 
-inherit base openib toolchain-funcs
+inherit openib toolchain-funcs
 
 DESCRIPTION="OpenIB userspace rds-tools"
 
 KEYWORDS="amd64 ~x86 ~amd64-linux"
-IUSE=""
 
 DEPEND="sys-fabric/libibverbs:${SLOT}"
-RDEPEND="${DEPEND}
-	!sys-fabric/openib-userspace"
+RDEPEND="
+	${DEPEND}
+	!sys-fabric/openib-userspace
+"
+
 block_other_ofed_versions
 
 DOCS=( README )