openrisc: remove HAVE_VIRT_TO_BUS

The OpenRISC arch doesn't actually have the virt_to_bus methods
Signed-off-by: Jonas Bonn <jonas@southpole.se>

arch/openrisc/Kconfig

@@ -12,7 +12,6 @@ config OPENRISC
 	select ARCH_REQUIRE_GPIOLIB
         select HAVE_ARCH_TRACEHOOK
 	select HAVE_GENERIC_HARDIRQS
-	select VIRT_TO_BUS
 	select GENERIC_IRQ_CHIP
 	select GENERIC_IRQ_PROBE
 	select GENERIC_IRQ_SHOW