block: rnull: remove imports available via prelude

These imports are already in scope by importing `kernel::prelude::*` and
does not need to be imported separately.

Signed-off-by: Gary Guo <gary@garyguo.net>
Acked-by: Andreas Hindborg <a.hindborg@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

drivers/block/rnull/configfs.rs

@@ -13,7 +13,6 @@ use kernel::{
     str::{kstrtobool_bytes, CString},
     sync::Mutex,
 };
-use pin_init::PinInit;
 
 pub(crate) fn subsystem() -> impl PinInit<kernel::configfs::Subsystem<Config>, Error> {
     let item_type = configfs_attrs! {

drivers/block/rnull/rnull.rs

@@ -14,12 +14,9 @@ use kernel::{
             Operations, TagSet,
         },
     },
-    error::Result,
-    pr_info,
     prelude::*,
     sync::{aref::ARef, Arc},
 };
-use pin_init::PinInit;
 
 module! {
     type: NullBlkModule,