riscv: Don't duplicate _ALTERNATIVE_CFG* macros

Reduce clutter by only defining the _ALTERNATIVE_CFG* macros once,
rather than once for assembly and once for C. To do that, we need to
add __ALTERNATIVE_CFG* macros to the assembly side, but those are
one-liners. Also take the opportunity to do a bit of reformatting,
taking full advantage of the fact checkpatch gives us 100 char lines.

Signed-off-by: Andrew Jones <ajones@ventanamicro.com>
Tested-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20221129150053.50464-5-ajones@ventanamicro.com


Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>