powerpc/irq: We don't need __do_IRQ() anymore

So select GENERIC_HARDIRQS_NO__DO_IRQ to disable it.
Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/Kconfig

@@ -42,6 +42,10 @@ config GENERIC_HARDIRQS
 	bool
 	default y
 
+config GENERIC_HARDIRQS_NO__DO_IRQ
+	bool
+	default y
+
 config HAVE_SETUP_PER_CPU_AREA
 	def_bool PPC64