kgdb: rectify kernel-doc for kgdb_unregister_io_module()

The command 'find ./kernel/debug/ | xargs ./scripts/kernel-doc -none'
reported a typo in the kernel-doc of kgdb_unregister_io_module().

Rectify the kernel-doc, such that no issues remain for ./kernel/debug/.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Link: https://lore.kernel.org/r/20210125144847.21896-1-lukas.bulwahn@gmail.comSigned-off-by: Daniel Thompson <daniel.thompson@linaro.org>

kernel/debug/debug_core.c

@@ -1166,7 +1166,7 @@ int kgdb_register_io_module(struct kgdb_io *new_dbg_io_ops)
 EXPORT_SYMBOL_GPL(kgdb_register_io_module);
 
 /**
- *	kkgdb_unregister_io_module - unregister KGDB IO module
+ *	kgdb_unregister_io_module - unregister KGDB IO module
  *	@old_dbg_io_ops: the io ops vector
  *
  *	Unregister it with the KGDB core.