FSyncControl: Fix warning
/project/android/kernel/jalte2/drivers/misc/fsync_control.c:19:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
 bool fsynccontrol_fsync_enabled()
      ^
/project/android/kernel/jalte2/drivers/misc/fsync_control.c:23:1: warning: data definition has no type or storage class
 EXPORT_SYMBOL(fsynccontrol_fsync_enabled);
 ^
/project/android/kernel/jalte2/drivers/misc/fsync_control.c:23:1: warning: type defaults to ‘int’ in declaration of ‘EXPORT_SYMBOL’ [-Wimplicit-int]
/project/android/kernel/jalte2/drivers/misc/fsync_control.c:23:1: warning: parameter names (without types) in function declaration