drm/i915/display: Mark conn as initialised by iterator

smatch complains about
drivers/gpu/drm/i915//display/intel_display.c:14403 intel_set_dp_tp_ctl_normal() error: uninitialized symbol 'conn'.
because it has no way to determine that the loop must have an entry.
Tell the static analysers to ignore the local, it will always be set.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191028142652.1987-2-chris@chris-wilson.co.uk