MIPS: import optimized string functions from Linux
10x performance gain according to simple test on QEMU malta:
barebox:/ time memcpy 0xa0000000 0xa0001000 0x100000
Signed-off-by: Aleksey Kuleshov <rndfax@yandex.ru>
Acked-by: Antony Pavlov <antonynpavlov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>