platform/x86: thinkpad_acpi: remove unused defines

They were never used.
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/thinkpad_acpi.c

@@ -9318,9 +9318,6 @@ static struct ibm_struct mute_led_driver_data = {
 #define GET_STOP	"BCSG"
 #define SET_STOP	"BCSS"
 
-#define START_ATTR "charge_start_threshold"
-#define STOP_ATTR  "charge_stop_threshold"
-
 enum {
 	BAT_ANY = 0,
 	BAT_PRIMARY = 1,