fbdev: remove the unnecessary includes of ppc specific header files

In the current kernel, we don't need to include these arch specific
header files for ppc.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Acked-by: Tomi Valkeinen <tomi.valkeinen@ti.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>