mn10300: tidy pic address loading

mn10300: tidy pic address loading

There's little reason to greatly complicate things by splitting
the pic_load patterns and using complex rtl to make it work out.
Instead, use the %= marker to generate unique numbers and emit
the entire load_pic sequence at once.

At the same time, collect all references to outgoing_args_size
into mn10300_frame_size, and all computations of register save
area size into mn10300_initial_offset.

From-SVN: r169012