scsi: ufs: add tracing support

This change adds the ftrace support for following:
1. UFS initialization time
2. Clock gating states
3. Clock scaling states
4. Power management APIs latency
5. BKOPs enable/disable

Usage:
	echo 1 > /sys/kernel/debug/tracing/events/ufs/enable
	cat /sys/kernel/debug/tracing/trace_pipe

Reviewed-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: Subhash Jadavani <subhashj@codeaurora.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>