In order to provide better reviewer suggestions and to introduce fine
grained additional approval permissions, sprinkle some OWNERS files over
the tree.

This essentially grants additional OWNERS permissions in
  - net/
  - arch/arm*/net
  - arch/x86/net
  - drivers/net
  - fs/crypto
  - fs/f2fs
  - fs/verity

All other permissions are already covered by ref/meta/config:OWNERS.

Signed-off-by: Matthias Maennich <maennich@google.com>
Change-Id: I02a6563e4dd63842af37c50f7180bf38e9b9b4be