wlcore: allow setting sleep_auth before interface init

Hold a value for sta_sleep_auth that is amenable to change by debugfs.
When detecting a legal value in this variable on interface init, use it
as an override value for sleep_auth.

This makes debugging more intuitive using the debugfs value.

Increment the conf version since we added an element to the conf
structure.

Note: An AP going up will always set sleep_auth to PSM_CAM.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Luciano Coelho <coelho@ti.com>