std/os: define and use dev_t for linux x86_64

Author: ifreund

lib/std/os/bits/linux/x86_64.zig

@@ -512,18 +512,19 @@ pub const msghdr_const = extern struct {
 
 pub const off_t = i64;
 pub const ino_t = u64;
+pub const dev_t = u64;
 
 // The `stat` definition used by the Linux kernel.
 pub const kernel_stat = extern struct {
-    dev: u64,
+    dev: dev_t,
     ino: ino_t,
     nlink: usize,
 
     mode: u32,
     uid: uid_t,
     gid: gid_t,
     __pad0: u32,
-    rdev: u64,
+    rdev: dev_t,
     size: off_t,
     blksize: isize,
     blocks: i64,