Drop SR_CONF_SET flag from SR_CONF_CONTINUOUS options

Drop SR_CONF_SET flag from SR_CONF_CONTINUOUS options

SR_CONF_CONTINUOUS is a capability option indicating whether a device
supports continuous capture or not. If the option exists the device
supports continuous capture and otherwise it doesn't. There is no value
associated with it and hence setting the SR_CONF_SET flag is nonsensical.

None of the drivers which set SR_CONF_SET for SR_CONF_CONTINUOUS handle it
in their config_set() callback and return an error if an application tried
to perform a config_set() operation for SR_CONF_CONTINUOUS.

Simply remove the SR_CONF_SET flag from all SR_CONF_CONTINUOUS options.

Signed-off-by: Lars-Peter Clausen <redacted>