Did Dally die because he wanted to die?

The fact that Dally's death was a suicide isn't difficult to discern. You don't rob a store and then proceed to pull a gun on officers of the law without knowing you're going to get shot. Dally wasn't ignorant, he knew what would happen.... This is also corroborated by Ponyboy in the following statement.

He was dead before he hit the ground. But I knew that was what he wanted, even as the lot echoed with the cracks of the shots, even as I begged silently – Please not him […] I knew he would be dead because Dallas Winston wanted to be dead and he always got what he wanted.