riscv: alternatives: fix a typo in comment

In the usage of ALTERNATIVE, "always" is misspelled as "alwyas".

Signed-off-by: Yuan Tan <tanyuan@tinylab.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230723165155.4896-1-tanyuan@tinylab.org


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