Fix comment on constructor parameter

Change-Id: I29d19188f189d2c2ff7b70058782cf7a89e1dabd
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/93820
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: Ben Clayton <bclayton@google.com>
Auto-Submit: David Neto <dneto@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>

src/tint/reader/spirv/function.h

@@ -241,8 +241,8 @@ enum class SkipReason {
 struct DefInfo {
     /// Constructor.
     /// @param def_inst the SPIR-V instruction defining the ID
-    /// @param locally_defined the SPIR-V instruction defining the ID
-    /// @param block_pos the position of the basic block where the ID is defined.
+    /// @param locally_defined true if the defining instruction is in the function
+    /// @param block_pos the position of the basic block where the ID is defined
     /// @param index an ordering index for this local definition
     DefInfo(const spvtools::opt::Instruction& def_inst,
             bool locally_defined,