runtime: fix typo in comment

GitHub-Last-Rev: d6a6fa39095cac8a9acfeacbbafd636e1aa9b55b
GitHub-Pull-Request: golang/go#23809
Change-Id: Ife18ba2f982b5e1c30bda32d13dcd441778b986a
Reviewed-on: https://go-review.googlesource.com/93575Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/runtime/internal/atomic/atomic_mipsx.go

@@ -25,7 +25,7 @@ func spinUnlock(state *uint32)
 
 //go:nosplit
 func lockAndCheck(addr *uint64) {
-	// ensure 8-byte alignement
+	// ensure 8-byte alignment
 	if uintptr(unsafe.Pointer(addr))&7 != 0 {
 		addr = nil
 	}