[i915] Fix driver from cliprects changes, and clean up state emission.

[i915] Fix driver from cliprects changes, and clean up state emission.

The fix for pageflipping with cliprects ended up causing a batch flush at
an inopportune time, which is fixed by moving it up.

Additionally, the recovery code for handling batch wraps at bad times is
replaced by just checking for the space up front, and using a no_batch_wrap
assert like on 965 to make sure that we weren't wrong about how much space that
was.