bus: mhi: core: Download AMSS image from appropriate function

During full boot chain firmware download, the PM state worker
downloads the AMSS image after a blocking wait for the SBL
execution environment change when running in PBL transition
itself. Improve this design by having the host download the AMSS
image from the SBL transition of PM state worker thread when a
DEV_ST_TRANSITION_SBL is queued instead of the blocking wait.

Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>
Reviewed-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Reviewed-by: Loic Poulain <loic.poulain@linaro.org>
Link: https://lore.kernel.org/r/1614208985-20851-3-git-send-email-bbhatt@codeaurora.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>