bus: mhi: core: Introduce counters to track MHI device state transitions

bus: mhi: core: Introduce counters to track MHI device state transitions

Use counters to track MHI device state transitions such as those
to M0, M2, or M3 states. This can help in better debug, allowing
the user to see the number of transitions to a certain MHI state
when queried using debugfs entries or via other mechanisms.

Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/20200929175218.8178-9-manivannan.sadhasivam@linaro.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>