My 15 month old dd still usually has two naps a day. 9.30-11.00am (I wake her, she'd sleep for longer), then usually 1.00-3.00 (I'm tied by the school run for this one).
Although I am aware this is unusual. By 12 months old my older 3 children had all moved to a single afternoon nap.
I would be guided by nighttime sleep. My dd sleeps 12 hours, sometimes longer. 7.00/7.30pm to 7.00/8.00am. If her nighttime sleep started getting affected, then I'd something about it. Otherwise I'm just going to let the transition to 1 nap happen naturally when she's ready.
Therefore I don't see 2 naps a day as a problem in my 15 month old.
However if I was dealing with a 5.30/6.00am wake up like you (assuming this isn't a convenient wake up time) then I would be aiming to change something. In your situation I would try gradually pushing morning nap later, moving it forward by 10/15 minutes every week or so. Then limit afternoon nap accordingly so that bedtime is unaffected.
Eventually you'll get to a point where you (or nursery) can make lunchtime early, say 11am and then nap straight after lunch.
You can then start gradually moving lunchtime later to push it to a more acceptable time (say 12.30) and nap afterwards.