i965: Fix the untyped surface opcodes to deal with indirect surface access.

i965: Fix the untyped surface opcodes to deal with indirect surface access.

Change brw_untyped_atomic() and brw_untyped_surface_read() to take the
surface index as a register instead of a constant and to use
brw_send_indirect_message() to emit the indirect variant of send with
a dynamically calculated message descriptor.  This will be required to
support variable indexing of image arrays for
ARB_shader_image_load_store.

Acked-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>