gpiolib: acpi: remove redundant declaration

Remove acpi_device declaration, as it is no longer needed.
Signed-off-by: Raag Jadav <raag.jadav@intel.com>
Reviewed-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/gpio/gpiolib-acpi.h

@@ -14,7 +14,6 @@
 
 #include <linux/gpio/consumer.h>
 
-struct acpi_device;
 struct device;
 struct fwnode_handle;