drm/i915: change i915_sw_fence license to MIT

Change the license of the i915_sw_fence files to MIT matching
most of the other i915 files.  This makes it possible to use them
in a new port of i915 to OpenBSD.

Besides some mechanical tree wide changes Chris Wilson is the sole
author of these files with Intel holding the copyright.

Intel's legal team have given permission to change the license according
to Joonas Lahtinen.

v2: expand commit message and note permission from Intel legal

Signed-off-by: Jonathan Gray <jsg@jsg.id.au>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Link: https://patchwork.freedesktop.org/patch/msgid/20181129013051.17525-1-jsg@jsg.id.au