powerpc: use kbuild generic-y where possible

Replace one line asm-generic include files declared in
arch/powerpc/include/asm/ by generic-y declaration
which creates arch/powerpc/include/generated/asm equivalent.

Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/include/asm/Kbuild

@@ -1,6 +1,8 @@
-
 generic-y += clkdev.h
+generic-y += div64.h
+generic-y += irq_regs.h
 generic-y += irq_work.h
+generic-y += local64.h
 generic-y += mcs_spinlock.h
 generic-y += preempt.h
 generic-y += rwsem.h