EDAC is still causing a few problems and the code is relatively green.  Mark
it as experimental until thing settle down.

Also, provide some documentation pointers in Kconfig help.
Signed-off-by: NTim Small <tim@buttersideup.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>