mm: License cleanup

Rik!

As you might know we are working on cleaning up the licensing mess in the
kernel and convert it to SPDX license identifiers as the only source of
license information.

Archaeology found the following unspecific GPL license reference, which
have been authored by you:

  mm/rmap.c: released under the general public license (gpl)

Can you please either send a cleanup patch or indicate which GPLv2 variant
you had in mind and I run it through my cleanup machinery.

Thanks,

	Thomas