LICENSES: Add MPL-1.1 license

Add the full text of the Mozilla Public License 1.1 to the kernel tree.  It was
copied directly from:

       https://spdx.org/licenses/MPL-1.1.html#licenseText

Signed-off-by: Thomas Gleixner <[email protected]>
Reviewed-by: Philippe Ombredanne <[email protected]>
Reviewed-by: Kate Stewart <[email protected]>
Reviewed-by: Greg Kroah-Hartman <[email protected]>
Signed-off-by: Jonathan Corbet <[email protected]>