How can you get your employees to see you as something other than a boss? You can't. Not while remaining a boss.
You need to determine what is more important to you.
If you want to advance in your career, make more money, have more responsibility, then you need to accept the fact that people will treat you differently. Your old peers are no longer your peers. Some will be more guarded around you, and some may try to take advantage of the situation by presuming that you'll overlook things that they're doing wrong, or they'll expect you to treat them differently (special privileges, etc.) because you had a previous "buddies" relationship. Those types of reactions are basic human nature; they transcend industry and culture, and you need to expect - and accept - that they will happen if you are moved to a supervisory position. It will then be your job to deal with them in a professional manner, which may not be the thing that some of your friends expect.
If maintaining your existing relationships "as-is" is more important to you, you'll need to try to return to your previous position as @JoeT mentioned in his comment. Other alternatives are to find another job and maintain the friendships (which can be difficult) or keep the supervisory role and accept that some friendships may suffer.
It's not fair to your friends or to your employer, though, to accept a supervisory role and then try to somehow act as if you're not a supervisor so that people won't treat you differently. That won't work; it will just confuse your direct reports and anger your management.