rmnet: Add export for rmnet_freq traces

Export was not added to rmnet_freq traces causing rmnet_shs to
not be able to use them.

This change exports rmnet_shs_freq traces to allow rmnet_shs the
ability to use the traces.

CRs-Fixed: 2437410
Change-Id: I9c26ad025fa2ee410abc580b717d2d858955ed3c
Acked-by: Raul Martinez <mraul@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>