rust: block: remove RawWriter

`RawWriter` is now dead code, so remove it.

Signed-off-by: Andreas Hindborg <[email protected]>

Author: Andreas Hindborg

rust/kernel/block/mq.rs

@@ -89,7 +89,6 @@
 
 pub mod gen_disk;
 mod operations;
-mod raw_writer;
 mod request;
 mod tag_set;