i915: fix compiler warning

The last i915 drm update brought with it this annoying warning

  drivers/gpu/drm/i915/intel_crt.c: In function ‘intel_crt_get_config’:
  drivers/gpu/drm/i915/intel_crt.c:110:21: warning: unused variable ‘dev’ [-Wunused-variable]
    struct drm_device *dev = encoder->base.dev;
                       ^

introduced by commit 7195a50b ("drm/i915: Add HSW CRT output readout
support").

Remove the offending pointless variable.
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/gpu/drm/i915/intel_crt.c

@@ -107,8 +107,6 @@ static unsigned int intel_crt_get_flags(struct intel_encoder *encoder)
 static void intel_crt_get_config(struct intel_encoder *encoder,
 				 struct intel_crtc_config *pipe_config)
 {
-	struct drm_device *dev = encoder->base.dev;
-
 	pipe_config->adjusted_mode.flags |= intel_crt_get_flags(encoder);
 }