nit, cleanup uses (#7747)

automerge

programs/bpf_loader/src/alloc.rs

@@ -1,5 +1,4 @@
-use std::alloc::Layout;
-use std::fmt;
+use std::{alloc::Layout, fmt};
 
 /// Based loosely on the unstable std::alloc::Alloc trait
 pub trait Alloc {

programs/bpf_loader/src/helpers.rs

@@ -7,12 +7,14 @@ use solana_rbpf::{
     memory_region::{translate_addr, MemoryRegion},
     EbpfVm,
 };
-use std::alloc::Layout;
-use std::ffi::CStr;
-use std::io::{Error, ErrorKind};
-use std::mem;
-use std::slice::from_raw_parts;
-use std::str::from_utf8;
+use std::{
+    alloc::Layout,
+    ffi::CStr,
+    io::{Error, ErrorKind},
+    mem,
+    slice::from_raw_parts,
+    str::from_utf8,
+};
 
 /// Program heap allocators are intended to allocate/free from a given
 /// chunk of memory.  The specific allocator implementation is

programs/bpf_loader/src/lib.rs

@@ -14,10 +14,11 @@ use solana_sdk::{
     pubkey::Pubkey,
     sysvar::rent,
 };
-use std::convert::TryFrom;
-use std::io::prelude::*;
-use std::io::Error;
-use std::mem;
+use std::{
+    convert::TryFrom,
+    io::{prelude::*, Error},
+    mem,
+};
 
 solana_sdk::declare_program!(
     solana_sdk::bpf_loader::ID,