Now that enumerations are available, any variable named "pin" can only
be used to describe a gpio pin. Rename the end_stop_state "pin"
parameter to "pin_value". Also, rename "end_stop_query" command to
"end_stop_query_state" to notify users to upgrade both host and mcu
code.
Signed-off-by: Kevin O'Connor <kevin@koconnor.net>