tty: Replace inline #ifdef TTY_DEBUG_WAIT_UNTIL_SENT

Add tty_debug_wait_until_sent() macro which uses tty_debug() to print
the debug message; remove inlined #ifdef.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>