dim: stop using Cc: drm-intel-fixes in dim fixes and cherry-pick-fixes

Nowadays our process relies on the Fixes: line, and Cc: drm-intel-fixes
is redundant. Stop adding and using it.

Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>