msm: tracing: Add ftrace support for LPM driver

Add trace event support to capture various parameters
of low power modes like power collapse, standalone power
collapse, retention and wfi during its entry and exit.

Change-Id: I0f8b918702ae47b354aa193aa7ef20b48110fb0f
Signed-off-by: Priyanka Mathur <pmathur@codeaurora.org>