drm/i915: fix error path in intel_setup_gmbus()

This fails to undo the setup for pin==0; moreover, something
interesting happens if the setup failed already at pin==0.

Signed-off-by: Rasmus Villemoes <[email protected]>
Fixes: f899fc6 ("drm/i915: use GMBUS to manage i2c links")
Cc: [email protected]
Signed-off-by: Jani Nikula <[email protected]>
Link: http://patchwork.freedesktop.org/patch/msgid/[email protected]

drivers/gpu/drm/i915/intel_i2c.c

@@ -683,7 +683,7 @@ int intel_setup_gmbus(struct drm_device *dev)
 	return 0;
 
 err:
-	while (--pin) {
+	while (pin--) {
 		if (!intel_gmbus_is_valid_pin(dev_priv, pin))
 			continue;