Introduced /proc/sys/dev/sensors/chips file

See doc/sysctl for an explanation why it is needed.

Also fixed two very small cleanup bugs in lm75/lm78, which would probably be
impossible to trigger anyway, but still.


git-svn-id: http://lm-sensors.org/svn/lm-sensors/trunk@51 7894878c-1315-0410-8ee3-d5d059ff63e0

doc/sysctl

@@ -0,0 +1,11 @@
+You can access everything under /proc/sys through the sysctl interface. This
+is mostly useful for C programs, which can use the sysctl function. Try
+'man 2 sysctl' for more information.
+
+As each chip gets its own directory under /proc/sys/dev/sensors, you must
+somehow know the sysctl id of these directories to access the sensor data.
+This is done through the file /proc/sys/dev/sensors/chips (see sensors.h
+for the corresponding SYSCTL ids). You can only read this file; it 
+returns an array of struct sensors_chips_data, as defined in sensors.h.
+Each chip will have its own entry here, with both its sysctl id and
+the corresponding /proc name.