i965: Rename do_<stage>_prog to brw_compile_<stage>_prog (and export)

i965: Rename do_<stage>_prog to brw_compile_<stage>_prog (and export)

This is in preparation for these functions to be called from other
files.

This commit is intended to have no functional change. It exists in
preparation for some upcoming code movement in preparation for the
shader cache.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>