i965/fs: Don't use instruction list after calculating the cfg.

i965/fs: Don't use instruction list after calculating the cfg.

The only trick is changing a break into a return true in register
coalescing, since the macro is actually a double loop, and break will do
something different than you expect. (Wish I'd realized that earlier!)

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>