According to commit f6b6f3c from
git://git.freescale.com/imx/uboot-imx.git:

	Also set Prefetch offset to 15, since it improves
	memcpy performance by 35%. Don't enable Incr double
	Linefill enable since it adversely affects memcpy
	performance by about 32MB/s and reads by 90MB/s. Tested
	with 4K to 16MB sized src and dst aligned buffer.

This commit ports those chagnes from U-Boot.

Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>