kernel: fix rustdoc links

kernel/src/syscall.rs

@@ -375,8 +375,10 @@ impl Syscall {
 ///
 /// This struct operates over primitive types such as integers of fixed length
 /// and pointers. It is constructed by the scheduler and passed down to the
-/// architecture to be encoded into registers, using the provided
-/// [`encode_syscall_return`](SyscallReturn::encode_syscall_return) method.
+/// architecture to be encoded into registers. Architectures may use the various
+/// helper functions defined in
+/// [`utilities::arch_helpers`](crate::utilities::arch_helpers), but are free to
+/// define their own ABI and encoding.
 ///
 /// Capsules do not use this struct. Capsules use higher level Rust types (e.g.
 /// [`ReadWriteProcessBuffer`](crate::processbuffer::ReadWriteProcessBuffer) and

kernel/src/utilities/arch_helpers.rs

@@ -244,7 +244,7 @@ pub fn encode_syscall_return_32bit_trd104(
 }
 
 /// Enumeration of all system call return type variant identifiers, as a
-/// superset of those defined in [`TRD104`]. This is not yet standardized.
+/// superset of those defined in TRD 104. This is not yet standardized.
 ///
 /// Each variant is associated with the respective variant identifier that would
 /// be passed along with the return value to userspace.