freedreno/ir3/ra: make use()/def() functions instead of macros

freedreno/ir3/ra: make use()/def() functions instead of macros

Originally these were nested functions, which worked nicely, giving us
the function of a local macro that was actual 'c' syntax (ie. not token
pasted macro).  But these were converted to macros because clang doesn't
let us have nice gcc extensions.

Extract these back out into functions, before adding more things and
making the macros even more cumbersome.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3569>