TIOCSTI: Document CAP_SYS_ADMIN behaviour in Kconfig

Clarifies that the LEGACY_TIOCSTI setting is safe to turn off even
when running BRLTTY, as it was introduced in commit 690c8b80
("TIOCSTI: always enable for CAP_SYS_ADMIN").

Signed-off-by: Günther Noack <gnoack3000@gmail.com>
Reviewed-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
Link: https://lore.kernel.org/r/20230808201115.23993-1-gnoack3000@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>