drivers/tty: remove redundant assignment to variable i and rename it to ret

drivers/tty: remove redundant assignment to variable i and rename it to ret

The variable i is being assigned a value that is never read
and it is being updated later with a new value. The assignment
is redundant and can be removed.  Also rename i to ret as this new
name makes makes more sense.

Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Acked-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20200405135423.383466-1-colin.king@canonical.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>