drm/i915: fix up the relocate_entry refactoring

Somehow we've lost the error handling in the patch split-up between
the internal and external patch. This regression has been introduced
in

commit 5032d871f7d300aee10c309ea004eb4f851553fe
Author: Rafael Barbalho <[e-mail]>
Date: Wed Aug 21 17:10:51 2013 +0100

drm/i915: Cleaning up the relocate entry function

This bug is exercised by igt/gem_reloc_vs_gpu/interruptible.

Cc: Rafael Barbalho <[e-mail]>
Signed-off-by: Daniel Vetter <[e-mail]>

drivers/gpu/drm/i915/i915_gem_execbuffer.c

···
 	else
 		ret = relocate_entry_gtt(obj, reloc);
 
+	if (ret)
+		return ret;
+
 	/* and update the user's relocation entry */
 	reloc->presumed_offset = target_offset;