platform/x86: alienware-wmi: Remove header duplicate

No need to #include <linux/acpi.h> twice. Remove second occurrence.
Signed-off-by: NAndy Shevchenko <andriy.shevchenko@linux.intel.com>

drivers/platform/x86/alienware-wmi.c

@@ -21,7 +21,6 @@
 #include <linux/module.h>
 #include <linux/platform_device.h>
 #include <linux/dmi.h>
-#include <linux/acpi.h>
 #include <linux/leds.h>
 
 #define LEGACY_CONTROL_GUID		"A90597CE-A997-11DA-B012-B622A1EF5492"