riscv: Make riscv_isa_vendor_ext_andes array static

Since this array is only used in this file, it should be static.

Signed-off-by: Charlie Jenkins <charlie@rivosinc.com>
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202407241530.ej5SVgX1-lkp@intel.com/


Reviewed-by: Alexandre Ghiti <alexghiti@rivosinc.com>
Link: https://lore.kernel.org/r/20240807-make_andes_static-v1-1-b64bf4c3d941@rivosinc.com


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