docbook: don't reference file without kernel-doc

Remove include/linux/rmap.h from kernel-api.tmpl since it no longer
contains kernel-doc.  Fixes this warning:

Warning(linux-2.6.22//include/linux/rmap.h): no structured comments found
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/DocBook/kernel-api.tmpl

@@ -159,7 +159,6 @@ X!Ilib/string.c
 !Earch/i386/lib/usercopy.c
      </sect1>
      <sect1><title>More Memory Management Functions</title>
-!Iinclude/linux/rmap.h
 !Emm/readahead.c
 !Emm/filemap.c
 !Emm/memory.c