msm: mhi: Fix issues regarding BHI img load

Resolve issue regarding BHI image load process.
Interface will no longer be published to userspace
before local initialization is complete.
Register masks and retry mechanism are also cleaned up.

Change-Id: I05d87d4be5e9c05c6beb2b7b0c0234757b93097d
Signed-off-by: Andrei Danaila <adanaila@codeaurora.org>