[MTD] [NOR] fix cfi_cmdset_0001 FL_SYNCING race (take 2)

The patch fixes CFI issue with multipartitional devices leading to the
set of errors or even deadlock. The problem is CFI FL_SYNCING state race
with flash operations (e.g. erase suspend). It is reproduced by running
intensive writes on one JFFS2 partition and simultaneously performing
mount/unmount cycle on another partition of the same chip.

Signed-off-by: Alexander Belyakov <abelyako@googlemail.com>
Acked-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>