ACPI: thinkpad-acpi: fix sysfs paths in documentation

The documentation used "thinkpad-acpi" to refer to the directories in
sysfs, while it should have been using "thinkpad_acpi".  Thanks to Hugh
Dickins for the error report.

I wish I could just call the module and everything else by the proper
name with the "-", instead of using these ugly translations to "_".
Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Cc: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Len Brown <len.brown@intel.com>

Documentation/thinkpad-acpi.txt

@@ -105,10 +105,10 @@ The version of thinkpad-acpi's sysfs interface is exported by the driver
 as a driver attribute (see below).
 
 Sysfs driver attributes are on the driver's sysfs attribute space,
-for 2.6.20 this is /sys/bus/platform/drivers/thinkpad-acpi/.
+for 2.6.20 this is /sys/bus/platform/drivers/thinkpad_acpi/.
 
 Sysfs device attributes are on the driver's sysfs attribute space,
-for 2.6.20 this is /sys/devices/platform/thinkpad-acpi/.
+for 2.6.20 this is /sys/devices/platform/thinkpad_acpi/.
 
 Driver version
 --------------