Set the buffer values in sceAtracSetHalfwayBuffer.

We set them in the GetID() one, so ought to here as well.

This is a minor change, and in fact doesn't overlap with #1263.  It does overlap with #997, which implements the same basic thing, but does a bit more.

This prevents "reading into 0" errors and the like in some games, like Zettai Hero Project, which expects `sceAtracGetStreamDataInfo()` to return a valid address after calling this func.  And ultimately that may help since sceIoRead() will return a value the game expects.

-[Unknown]