ARM: 7531/1: mark kernelmode mem{cpy,set} non-experimental

This feature was added in 2009, I've been using it off and on and
never had any problems with it on my systems. I cannot see why
it needs to be marked experimental, make it a normal feature and
let us discover its possible shortcomings as people try to turn
it on instead.

Cc: Lennert Buytenhek <kernel@wantstofly.org>
Cc: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>