rmnet: Add rmnet_shs freq traces

Add rmnet traces to be used in rmnet_shs's freq
boost feature.

Refactor existing rmnet_traces to use event class.

CRs-Fixed: 2437410
Change-Id: I44f42006a40b47ff7b083035732b47a1a78ece8c
Acked-by: Raul Martinez <mraul@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>