ANDROID: export mm_trace_rss_stat as gpl-only

The commit with change-id: Icb56b0c760780c3f9081f82d921406d17f4f1c08
exported mm_trace_rss_stat which is great, but as this change is not
upstream it needs to be exported as gpl-only.

Cc: Yongqin Liu <yongqin.liu@linaro.org>
Cc: Alistair Delva <adelva@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Ib72cf26a7824415b4beb5133c2cb477ec23d65c1