experimental/lib/tidl: Cast countof return value to uint32_t

The new definition of countof for C++ in compiler.h returns a size_t.

Bug: 230134581
Change-Id: I9f4808400f6d1a3ff237fc14b00daba40619ad58
diff --git a/experimental/lib/tidl/ipc.cpp b/experimental/lib/tidl/ipc.cpp
index 7b606df..59ccba7 100644
--- a/experimental/lib/tidl/ipc.cpp
+++ b/experimental/lib/tidl/ipc.cpp
@@ -103,7 +103,7 @@
             },
     };
     ipc_msg_t msg = {
-            .num_iov = countof(iovs),
+            .num_iov = static_cast<uint32_t>(countof(iovs)),
             .iov = iovs,
             .num_handles = num_handles,
             .handles = handles,
@@ -141,7 +141,7 @@
                 },
         };
         ipc_msg_t msg = {
-                .num_iov = countof(iovs),
+                .num_iov = static_cast<uint32_t>(countof(iovs)),
                 .iov = iovs,
                 .num_handles = num_handles,
                 .handles = handles,
@@ -177,7 +177,7 @@
             },
     };
     ipc_msg_t msg = {
-            .num_iov = countof(iovs),
+            .num_iov = static_cast<uint32_t>(countof(iovs)),
             .iov = iovs,
             .num_handles = num_handles,
             .handles = handles,
@@ -221,7 +221,7 @@
                 },
         };
         ipc_msg_t msg = {
-                .num_iov = countof(iovs),
+                .num_iov = static_cast<uint32_t>(countof(iovs)),
                 .iov = iovs,
                 .num_handles = num_handles,
                 .handles = handles,