ppc does not implement these, so remove the prototypes and use
the ones from include/linux/string.h

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Move platform independent header files to arch/ppc/include/asm, leaving
those in asm/arch*.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>