Fix "can not" in Documentation and Kconfig

Randy brought it to my attention that in proper english "can not" should always
be written "cannot". I donot see any reason to argue, even if I mightnot
understand why this rule exists.  This patch fixes "can not" in several
Documentation files as well as three Kconfigs.

Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>