Kernel: Remove unused madvise(MADV_GET_VOLATILE)

This was used to query the volatile state of a memory region, however
nothing ever actually used it.

Kernel/Syscalls/mmap.cpp

@@ -480,11 +480,6 @@ KResultOr<FlatPtr> Process::sys$madvise(Userspace<void*> address, size_t size, i
             return result.error();
         return was_purged ? 1 : 0;
     }
-    if (advice & MADV_GET_VOLATILE) {
-        if (!region->vmobject().is_anonymous())
-            return EPERM;
-        return static_cast<AnonymousVMObject&>(region->vmobject()).is_volatile() ? 0 : 1;
-    }
     return EINVAL;
 }
 

Kernel/UnixTypes.h

@@ -101,7 +101,6 @@ enum {
 
 #define MADV_SET_VOLATILE 0x100
 #define MADV_SET_NONVOLATILE 0x200
-#define MADV_GET_VOLATILE 0x400
 
 #define F_DUPFD 0
 #define F_GETFD 1

Userland/Libraries/LibC/sys/mman.h

@@ -29,7 +29,6 @@
 
 #define MADV_SET_VOLATILE 0x100
 #define MADV_SET_NONVOLATILE 0x200
-#define MADV_GET_VOLATILE 0x400
 
 __BEGIN_DECLS