[inc][utils] Add a utils.h for miscellaneous helpers

Add a utils.h file containing miscellaneous convenience helpers.

top/include/lk/utils.h

@@ -0,0 +1,21 @@
+/*
+ * SPDX-License-Identifier: MIT
+ *
+ * Copyright (C) 2020-2023 Google LLC.
+ */
+
+#pragma once
+
+#define ARRAY_SIZE(_a) (sizeof(_a) / sizeof(*(_a)))
+
+#define KB (1024UL)
+#define MB (1024UL * 1024UL)
+#define GB (1024UL * 1024UL * 1024UL)
+
+#define RETURN_IF_ERROR(expr) \
+        do { \
+            status_t err_ = (expr); \
+            if (err_ != NO_ERROR) { \
+                return err_; \
+            } \
+        } while (0)