[POWERPC] Clean out asm/of_{platform, device}.h from sysdev/

Convert #include of asm/of_{platform, device}.h into
linux/of_{platform,device}.h for remaining arch/powerpc files.

Signed-off-by: Jon Loeliger <jdl@freescale.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>