drm/i915: Pair va_copy with va_end in i915_error_vprintf

Each invocation of va_copy() must be matched by a corresponding
invocation of va_end() in the same function.

This regression has been introduced in

commit e29bb4ebbf000ff9ac081d29784a3331618f012e
Author: Chris Wilson <chris@chris-wilson.co.uk>
Date:   Fri Sep 20 10:20:59 2013 +0100

    drm/i915: Use a temporary va_list for two-pass string handling

Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gpu_error.c

@@ -146,7 +146,10 @@ static void i915_error_vprintf(struct drm_i915_error_state_buf *e,
 		va_list tmp;
 
 		va_copy(tmp, args);
-		if (!__i915_error_seek(e, vsnprintf(NULL, 0, f, tmp)))
+		len = vsnprintf(NULL, 0, f, tmp);
+		va_end(tmp);
+
+		if (!__i915_error_seek(e, len))
 			return;
 	}