Update err.h to get the assembler guards.

Corresponds to upstream fa9ee9c4b9885dfdf8eccac19b8b4fc8a7c53288.

Change-Id: If0030194a9049b7b84fec9a982b9bb0f136df4a6
diff --git a/original/linux/err.h b/original/linux/err.h
index cd3b367..f2edce2 100644
--- a/original/linux/err.h
+++ b/original/linux/err.h
@@ -15,21 +15,51 @@
  */
 #define MAX_ERRNO	4095
 
+#ifndef __ASSEMBLY__
+
 #define IS_ERR_VALUE(x) unlikely((x) >= (unsigned long)-MAX_ERRNO)
 
-static inline void *ERR_PTR(long error)
+static inline void * __must_check ERR_PTR(long error)
 {
 	return (void *) error;
 }
 
-static inline long PTR_ERR(const void *ptr)
+static inline long __must_check PTR_ERR(const void *ptr)
 {
 	return (long) ptr;
 }
 
-static inline long IS_ERR(const void *ptr)
+static inline long __must_check IS_ERR(const void *ptr)
 {
 	return IS_ERR_VALUE((unsigned long)ptr);
 }
 
+static inline long __must_check IS_ERR_OR_NULL(const void *ptr)
+{
+	return !ptr || IS_ERR_VALUE((unsigned long)ptr);
+}
+
+/**
+ * ERR_CAST - Explicitly cast an error-valued pointer to another pointer type
+ * @ptr: The pointer to cast.
+ *
+ * Explicitly cast an error-valued pointer to another pointer type in such a
+ * way as to make it clear that's what's going on.
+ */
+static inline void * __must_check ERR_CAST(const void *ptr)
+{
+	/* cast away the const */
+	return (void *) ptr;
+}
+
+static inline int __must_check PTR_RET(const void *ptr)
+{
+	if (IS_ERR(ptr))
+		return PTR_ERR(ptr);
+	else
+		return 0;
+}
+
+#endif
+
 #endif /* _LINUX_ERR_H */