drm/i915/crt: explicitly set up HOTPLUG_BITS on resume

... instead of relying on the register save/restore madness to do this.

To extract a bit of code call drm_mode_config_reset both on resume
and boot-up and move the hw state frobbing from the crt_init to the
->reset callback. The crt connector is the only one with a ->reset
callback, hence we can easily do this.

Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>