tty: whitespaces in descriptions corrected by replacing tabs with spaces

Tabs were used in the function description, to make this look more
uniform, the tabs were replaced by spaces where necessary.

While we're at it, I also replaced the 'ndashes' with simple dashes, since
only those are supported by sphinx.
Reviewed-by: Jiri Slaby <jirislaby@kernel.org>
Signed-off-by: Florian Eckert <fe@dev.tdt.de>
Link: https://lore.kernel.org/r/20231019112809.881730-2-fe@dev.tdt.deSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>