bus: mhi: core: Wait for ready after an EDL firmware download

Currently, the firmware load handler returns after the EDL image
is downloaded. Wait for an MHI READY transition instead as the
specification expects so as to proceed with further bootup such
as device entering Flash Programmer execution environment.

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/1617067704-28850-3-git-send-email-bbhatt@codeaurora.org


Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>