pw_allocator: Add missing includes

Change-Id: I122ecf4a24357678c9b0544015b1955aecd7693d
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/98900
Reviewed-by: Alexei Frolov <frolv@google.com>
Commit-Queue: Auto-Submit <auto-submit@pigweed.google.com.iam.gserviceaccount.com>
Pigweed-Auto-Submit: Dennis Kormalev <denk@google.com>
diff --git a/pw_allocator/block.cc b/pw_allocator/block.cc
index c673eb5..f477674 100644
--- a/pw_allocator/block.cc
+++ b/pw_allocator/block.cc
@@ -15,6 +15,7 @@
 #include "pw_allocator/block.h"
 
 #include <cstring>
+#include <span>
 
 #include "pw_assert/check.h"
 
diff --git a/pw_allocator/public/pw_allocator/block.h b/pw_allocator/public/pw_allocator/block.h
index 3edc92c..ba2e171 100644
--- a/pw_allocator/public/pw_allocator/block.h
+++ b/pw_allocator/public/pw_allocator/block.h
@@ -16,6 +16,7 @@
 // usable.
 #pragma once
 
+#include <cstdint>
 #include <span>
 
 #include "pw_status/status.h"