trace: rtb: add msm_rtb register tracing feature snapshot

This is a snapshot of the msm_rtb driver from kernel/trace taken as of
msm-4.4 commit <9d9cf7636c0d82> (Merge "clk: msm: clock-gpu-cobalt:
Update the GPU PLL FMAXes")

CRs-Fixed: 1055807
Change-Id: I8caff1efbebe1de0cd02c6d7ee7721ebec2d1de1
Signed-off-by: Bruce Levy <blevy@codeaurora.org>
Signed-off-by: Bhargav Gurappadi <bhargavg1@codeaurora.org>