i965: Use the batch save/reset code to avoid needing the BO validate step.

i965: Use the batch save/reset code to avoid needing the BO validate step.

We were doing the BO validate step in prepare() (brw_validate_state())
hooks of atoms so that we could check_aperture before emitting the
relocation trees during brw_upload_state() that would actually make
the batchbuffer reference too much memory to be executed.  Now that
all relocations occur in the batchbuffer, we can instead
check_aperture after emitting our state into the batchbuffer, and
easily roll back, flush, and retry if we happened to go over the
limits.

This will let us remove the whole prepare() vs emit() split in our
state atoms, which is a source of tricky dependencies and duplicated
code.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Acked-by: Paul Berry <stereotype441@gmail.com>