Kernel: Remove kfree(), leaving only kfree_sized() :^)

There are no more users of the C-style kfree() API in the kernel,
so let's get rid of it and enjoy the new world where we always know
how much memory we are freeing. :^)

Kernel/Heap/kmalloc.cpp

@@ -273,16 +273,12 @@ void* kmalloc(size_t size)
 }
 
 void kfree_sized(void* ptr, size_t size)
-{
-    (void)size;
-    return kfree(ptr);
-}
-
-void kfree(void* ptr)
 {
     if (!ptr)
         return;
 
+    VERIFY(size > 0);
+
     kmalloc_verify_nospinlock_held();
     SpinlockLocker lock(s_lock);
     ++g_kfree_call_count;