kgdb: configs: remove obsolete CONFIG_KGDB_SER_INDEX

The last users of CONFIG_KGDB_SER_INDEX were removed more than 3 years
ago in commits 550650ddd0 and bf16500f79, either kgdb subsystem should
care about this parameter or it should be gone completely.

Signed-off-by: Vladimir Zapolskiy <vz@mleia.com>
95 files changed