wm97xx_battery: Handle missing platform data gracefully

Don't unconditionally dereference the WM97xx core platform data since
it may not be present, causing an oops.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
1 file changed