openrisc: require gpiolib

The recent move to GPIO descriptors breaks the OpenRISC build.  Requiring
gpiolib resolves this; using gpiolib exclusively is also the recommended
way forward for all arches by the developers working on these GPIO changes.
The non-gpiolib implementation for OpenRISC never worked anyway...
Signed-off-by: Jonas Bonn <jonas@southpole.se>

arch/openrisc/Kconfig

@@ -9,7 +9,7 @@ config OPENRISC
 	select OF_EARLY_FLATTREE
 	select IRQ_DOMAIN
 	select HAVE_MEMBLOCK
-	select ARCH_WANT_OPTIONAL_GPIOLIB
+	select ARCH_REQUIRE_GPIOLIB
         select HAVE_ARCH_TRACEHOOK
 	select HAVE_GENERIC_HARDIRQS
 	select VIRT_TO_BUS