turnip: Convert renderpass setup to the new register packing macros.

turnip: Convert renderpass setup to the new register packing macros.

This gets a lot of the hard code converted over to the new macros,
resulting in (I feel) much more readable code with
LESS_SHOUTING_ABOUT_THE_REG().  I decided to consistently put the reg on
its own line, so that all the register names line up.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3455>