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>
diff --git a/mm/Kconfig b/mm/Kconfig
index f10fe51..db7c55d 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -92,7 +92,7 @@
 
 #
 # SPARSEMEM_EXTREME (which is the default) does some bootmem
-# allocations when memory_present() is called.  If this can not
+# allocations when memory_present() is called.  If this cannot
 # be done on your architecture, select this option.  However,
 # statically allocating the mem_section[] array can potentially
 # consume vast quantities of .bss, so be careful.