coda: ftoc validity check integration

coda: ftoc validity check integration

This patch moves cfi check in coda_ftoc() instead of repeating it in the
wild.

  Module size
     text	   data	    bss	    dec	    hex	filename
    28297	   1040	    700	  30037	   7555	fs/coda/coda.ko.before
    28263	    980	    700	  29943	   74f7	fs/coda/coda.ko.after

Link: http://lkml.kernel.org/r/a2c27663ec4547018c92d71c63b1dff4650b6546.1558117389.git.jaharkes@cs.cmu.edu
Signed-off-by: Fabian Frederick <fabf@skynet.be>
Signed-off-by: Jan Harkes <jaharkes@cs.cmu.edu>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Colin Ian King <colin.king@canonical.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Mikko Rapeli <mikko.rapeli@iki.fi>
Cc: Sam Protsenko <semen.protsenko@linaro.org>
Cc: Yann Droneaud <ydroneaud@opteya.com>
Cc: Zhouyang Jia <jiazhouyang09@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>