What is the file you are uploading? It should be a ZIP file.
Is there a reason you don't want to upgrade to 9.1.1 which is included in the software pack?
Nevermind, I doublechecked the release notes from 9.1.1SR1 which states:
For all SCCP firmware upgrades from firmware release versions earlier than 8.3(3) to version 8.5(2)SR1 or greater, you must first upgrade your firmware to version 8.5(2). Once you have upgraded to version 8.5(2), you can upgrade your IP Phone to version 9.1(1)SR1 or later.