kfifo: replace the old non generic API

Simply replace the whole kfifo.c and kfifo.h files with the new generic
version and fix the kerneldoc API template file.

Signed-off-by: Stefani Seibold <stefani@seibold.net>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/DocBook/kernel-api.tmpl

@@ -132,7 +132,6 @@ X!Ilib/string.c
      <title>FIFO Buffer</title>
      <sect1><title>kfifo interface</title>
 !Iinclude/linux/kfifo.h
-!Ekernel/kfifo.c
      </sect1>
   </chapter>