mhi: core: Move to error state if firmware could not be loaded

Move MHI to a firmware download error state for any bootup
failures such as unable to find firmware files or load images via
BHI/BHIe. This helps detect an error state sooner and shortens
the wait for a synchronous power up timeout. It also negates the
need to provide additional callbacks due to any intermediate
bootup failures.

Change-Id: I3307e432063f59e978f1e055453155803a6475b2
Signed-off-by: Bhaumik Bhatt <bbhatt@codeaurora.org>