mmc: core: Add tracepoints to enhance pm debugging

Instrument the mmc core layer with tracepoints to aid in
debugging issues and identifying latencies in the following
paths:
* System suspend/resume
* Runtime suspend/resume

Change-Id: I1e0fa7d3f8b54c102b4055f910b58a42412748da
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>