Fix broken SpinLock.

The SpinLock was all backwards and didn't actually work. Fixing it exposed
how wrong most of the locking here is.

I need to come up with a better granularity here.

VirtualFileSystem/DiskDevice.cpp

@@ -10,6 +10,7 @@ DiskDevice::~DiskDevice()
 
 bool DiskDevice::read(DiskOffset offset, unsigned length, byte* out) const
 {
+    //kprintf("DD::read %u x%u\n", offset, length);
     ASSERT((offset % blockSize()) == 0);
     ASSERT((length % blockSize()) == 0);
     dword firstBlock = offset / blockSize();