Make sure we update filtering options on atlas textures.

We had had an optimization which tried to reduce state changes,
but filtering is also changed in QSGTexture::updateBindOptions
which Atlas::bind() didn't know anything about. Solution: don't
try to be so clever.

Task-number: QTBUG-35457
Change-Id: I39ac0106396921e1b652db2b2aa5a9923b35e825
Reviewed-by: Shawn Rutledge <shawn.rutledge@digia.com>