Update result.rs

Adding the remaining ReturnCode values that exist in [tock/returncode.rs](https://github.com/tock/tock/blob/master/kernel/src/returncode.rs)

core/src/result.rs

diff --git a/core/src/result.rs b/core/src/result.rs
index 9508738..af4550c 100644
--- a/core/src/result.rs
+++ b/core/src/result.rs
@@ -25,6 +25,14 @@
 pub const FAIL: isize = -1;
 pub const EBUSY: isize = -2;
 pub const EALREADY: isize = -3;
+pub const EOFF: isize = -4;
+pub const ERESERVE: isize = -5;
 pub const EINVAL: isize = -6;
 pub const ESIZE: isize = -7;
+pub const ECANCEL: isize = -8;
 pub const ENOMEM: isize = -9;
+pub const ENOSUPPORT: isize = -10;
+pub const ENODEVICE: isize = -11;
+pub const EUNINSTALLED: isize = -12;
+pub const ENOACK: isize = -13;
+