riscv: Kconfig.socs: Add comments

Add trailing comments to endif and endmenu statements for better
readability.

Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Link: https://lore.kernel.org/r/20220520120232.148310-4-juergh@canonical.com


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