bus: mhi: core: Improvements to the channel handling state machine

bus: mhi: core: Improvements to the channel handling state machine

Improve the channel handling state machine such that all commands
go through a common function and a validation process to ensure
that the state machine is not violated in any way and adheres to
the MHI specification. Using this common function allows MHI to
eliminate some unnecessary debug messages and code duplication.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Link: https://lore.kernel.org/r/1617311778-1254-4-git-send-email-bbhatt@codeaurora.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>