Revert "tty: n_smux: Add function to determine if remote side is active"

This reverts commit 9359ddb5a2776f82b26d435395ecb95c4f7a57a0.
Revert "n_smux: add debugfs node for printing channel states"

This reverts commit 67b989665396bc1cfd0750a088aab74440a11062.

Signed-off-by: Paul Beeler <sparksco@gmail.com>

Conflicts:
	drivers/tty/smux_debug.c
Revert "Revert "tty: n_smux: Add function to determine if remote side is active""

This reverts commit 7d35f95d1c6e0b49359a968d7351c43e0534d043.