MAINTAINERS: put DYNAMIC INTERRUPT MODERATION in proper order

Commit 9b038086

 ("docs: networking: convert DIM to RST") added a new
file entry to DYNAMIC INTERRUPT MODERATION to the end, and not following
alphabetical order.

So, ./scripts/checkpatch.pl -f MAINTAINERS complains:

  WARNING: Misordered MAINTAINERS entry - list file patterns in alphabetic
  order
  #5966: FILE: MAINTAINERS:5966:
  +F:      lib/dim/
  +F:      Documentation/networking/net_dim.rst

Reorder the file entries to keep MAINTAINERS nicely ordered.

Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Acked-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>