drm/i915/skl: Rename a local variable to fit in 80 chars

No reason to not follow the 80 chars rule, renaming the local variable
makes it easy.

Cc: Chandra Konduru <chandra.konduru@intel.com>
Signed-off-by: Damien Lespiau <damien.lespiau@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>