r600g: Swap the util_blitter_destroy call order.

r600g: Swap the util_blitter_destroy call order.

Trivial change that avoids a segmentation fault when the blitter state
happens to be bound when the context is destroyed.

The free calls should probably removed altogether in the future -- the
responsibility to destroy the state atoms lies with whoever created it,
and the safest thing for the pipe driver is to not touch any bound state
in its destructor.