Kernel/SysFS: Don't compute exact size of PCI files

There's no need for generated files in SysFS to tell you their precise
file size when you stat() them.

I noticed when profiling "find /" that we were spending a chunk of time
generating and throwing away SysFS content just so we could tell you
exactly how large it would be. :^)

Kernel/Bus/PCI/Access.h

@@ -39,7 +39,6 @@ public:
 
     virtual KResultOr<size_t> read_bytes(off_t, size_t, UserOrKernelBuffer&, FileDescription*) const override;
     virtual ~PCIDeviceAttributeSysFSComponent() {};
-    virtual size_t size() const override;
 
 protected:
     virtual OwnPtr<KBuffer> try_to_generate_buffer() const;