ACPI: thinkpad-acpi: mark acpi helper functions __must_check

Mark acpi_evalf and friends __must_check.

Signed-off-by: Henrique de Moraes Holschuh <hmh@hmh.eng.br>
Signed-off-by: Len Brown <len.brown@intel.com>
diff --git a/drivers/misc/thinkpad_acpi.h b/drivers/misc/thinkpad_acpi.h
index 529528c..1b4cd16 100644
--- a/drivers/misc/thinkpad_acpi.h
+++ b/drivers/misc/thinkpad_acpi.h
@@ -97,11 +97,11 @@
 #define IBM_PCI_HID     "PNP0A03"
 
 /* ACPI helpers */
-static int acpi_evalf(acpi_handle handle,
+static int __must_check acpi_evalf(acpi_handle handle,
 		      void *res, char *method, char *fmt, ...);
-static int acpi_ec_read(int i, u8 * p);
-static int acpi_ec_write(int i, u8 v);
-static int _sta(acpi_handle handle);
+static int __must_check acpi_ec_read(int i, u8 * p);
+static int __must_check acpi_ec_write(int i, u8 v);
+static int __must_check _sta(acpi_handle handle);
 
 /* ACPI handles */
 static acpi_handle root_handle;			/* root namespace */