platform/x86: dell-wmi-sysman: fw_attr_inuse can be static

drivers/platform/x86/firmware_attributes_class.c:11:5: warning: symbol 'fw_attr_inuse' was not declared. Should it be static?
Reported-by: Nkernel test robot <lkp@intel.com>
Signed-off-by: Nkernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/20210603153936.GA65404@7832cb195c0bSigned-off-by: NHans de Goede <hdegoede@redhat.com>

drivers/platform/x86/firmware_attributes_class.c

@@ -8,7 +8,7 @@
 #include "firmware_attributes_class.h"
 
 static DEFINE_MUTEX(fw_attr_lock);
-int fw_attr_inuse;
+static int fw_attr_inuse;
 
 static struct class firmware_attributes_class = {
 	.name = "firmware-attributes",