fix map import to rustc_middle

Author: DevinR528

README.md

@@ -5,7 +5,7 @@
 
 A collection of lints to catch common mistakes and improve your [Rust](https://github.com/rust-lang/rust) code.
 
-[There are 363 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
+[There are 362 lints included in this crate!](https://rust-lang.github.io/rust-clippy/master/index.html)
 
 We have a bunch of lint categories to allow you to choose how much Clippy is supposed to ~~annoy~~ help you:
 

clippy_lints/src/if_let_mutex.rs

@@ -1,5 +1,5 @@
 use crate::utils::{match_type, paths, span_lint_and_help};
-use rustc::hir::map::Map;
+use rustc_middle::hir::map::Map;
 use rustc_hir::intravisit::{self as visit, NestedVisitorMap, Visitor};
 use rustc_hir::{Arm, Expr, ExprKind, MatchSource, StmtKind};
 use rustc_lint::{LateContext, LateLintPass};