power: supply: ab8500: Fix an old bug

Trying to get the AB8500 charging driver working I ran into a bit
of bitrot: we haven't used the driver for a while so errors in
refactorings won't be noticed.

This one is pretty self evident: use argument to the macro or we
end up with a random pointer to something else.

Cc: stable@vger.kernel.org
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Marcus Cooper <codekipper@gmail.com>
Fixes: 297d716f ("power_supply: Change ownership from driver to core")
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>

drivers/power/supply/ab8500-chargalg.h

@@ -15,7 +15,7 @@
  * - POWER_SUPPLY_TYPE_USB,
  * because only them store as drv_data pointer to struct ux500_charger.
  */
-#define psy_to_ux500_charger(x) power_supply_get_drvdata(psy)
+#define psy_to_ux500_charger(x) power_supply_get_drvdata(x)
 
 /* Forward declaration */
 struct ux500_charger;