Update ci/dma/examples/seven.rs

Co-Authored-By: japaric <[email protected]>

Author: korken89

ci/dma/examples/seven.rs

@@ -90,7 +90,7 @@ impl<B> Transfer<B> {
 
     /// Blocks until the transfer is done and returns the buffer
     pub fn wait(self) -> (Pin<B>, Serial1) {
-        while self.is_done() {}
+        while !self.is_done() {}
 
         atomic::compiler_fence(Ordering::Acquire);