dz: add and reorder inclusions, remove unneeded ones

Sort the header inclusions, add a few that are needed but pulled indirectly
only and remove ones that are not really used.

Signed-off-by: Maciej W. Rozycki <macro@linux-mips.org>
Cc: Jiri Slaby <jirislaby@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>