- Move open-coded filesystem magic numbers into magic.h

- Rearrange magic.h so that the filesystem-related constants are grouped
  together.
Signed-off-by: NMuthukumar R <muthur@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>