i965: Use brw_bo_wait() for brw_bo_wait_rendering()

i965: Use brw_bo_wait() for brw_bo_wait_rendering()

Currently, we use set_domain() to cause a stall on rendering. But the
set-domain ioctl has the side-effect of changing the kernel's cache
domain underneath the struct_mutex, which may perturb state if there was
no rendering to wait upon and in general is much heavier than the
lockless wait-ioctl. Historically libdrm used set-domain as we did not
have an explicit wait-ioctl (and the patches to teach it to use wait if
available were lost in the mists). Since mesa already depends upon a
kernel support the wait-ioctl, we do not need to supply a fallback.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>