ACPI / battery: minor tweaks to acpi_battery_units()

Make the acpi_battery_units() function take a const argument and return
a const char*, too. Also make it static. It probably doesn't matter, as
gcc will be clever enough to optimize and inline the code even without
these hints. However, we also get rid of a #ifdef block by moving the
function closer to its usage location, so it's at least a small gain in
code readability.

Signed-off-by: Mathias Krause <minipli@googlemail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/battery.c

@@ -339,14 +339,6 @@ static enum power_supply_property energy_battery_props[] = {
 	POWER_SUPPLY_PROP_SERIAL_NUMBER,
 };
 
-#ifdef CONFIG_ACPI_PROCFS_POWER
-inline char *acpi_battery_units(struct acpi_battery *battery)
-{
-	return (battery->power_unit == ACPI_BATTERY_POWER_UNIT_MA) ?
-		"mA" : "mW";
-}
-#endif
-
 /* --------------------------------------------------------------------------
                                Battery Management
    -------------------------------------------------------------------------- */
@@ -793,6 +785,12 @@ static void acpi_battery_refresh(struct acpi_battery *battery)
 #ifdef CONFIG_ACPI_PROCFS_POWER
 static struct proc_dir_entry *acpi_battery_dir;
 
+static const char *acpi_battery_units(const struct acpi_battery *battery)
+{
+	return (battery->power_unit == ACPI_BATTERY_POWER_UNIT_MA) ?
+		"mA" : "mW";
+}
+
 static int acpi_battery_print_info(struct seq_file *seq, int result)
 {
 	struct acpi_battery *battery = seq->private;