Frameworks/base: Fix AdapterViewAnimator.createOrReuseLayoutParams

The original code was certainly not wrong, but not readable. currentLp
was already an instance (ViewGroup.LayoutParams == LayoutParams), so the
instanceof is the same as a null check. Simplify.

Change-Id: I5ec96ab1243aa5f3a4d74a5fb991dded37c149c3