i965: Pass number of components explicitly to brw_untyped_atomic and _surface_read.

i965: Pass number of components explicitly to brw_untyped_atomic and _surface_read.

And calculate the message response size based on the number of
components rather than the other way around.  This simplifies their
interface somewhat and allows the caller to request a writeback
message with more than one vector component in SIMD4x2 mode.

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