i965: Move brw_get_shader_time_index() call out of emit functions

i965: Move brw_get_shader_time_index() call out of emit functions

brw_get_shader_time_index() is all tangled up in brw_context state and
we can't call it from the compiler. Thanks the Jasons recent
refactoring, we can just get the index and pass to the emit functions
instead.

Reviewed-by: Jason Ekstrand <jason.ekstrand@intel.com>
Signed-off-by: Kristian Høgsberg Kristensen <krh@bitplanet.net>