msm: rtb: Move RTB out of mach-msm

For compatability with new chips, there is a movement to move drivers
out of mach-msm. Move RTB to the tracing directory which is the closest
match for the RTB features.

Change-Id: I059289a0a66daf9a84e77c94d164887d07e167d5
Signed-off-by: Laura Abbott <lauraa@codeaurora.org>