i965: Initialize the intel_context::bufmgr pointer earlier.

i965: Initialize the intel_context::bufmgr pointer earlier.

This prevents a crash in a future patch.

_mesa_initialize_context() creates a default transform feedback object
by calling the NewTransformFeedbackObject() driver hook.  Eventually,
we'll want to subclass that and allocate a buffer object.  This means
passing brw->bufmgr to drm_intel_alloc_bo(), and crashing if it isn't
initialized yet.

The buffer manager is actually already initialized; we just hadn't
copied the pointer from intel_screen to intel_context quite early
enough.

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