MT#55283 version-guard static_assert

We don't have this available before kernel 5.1

Ref: https://bugs.debian.org/1101804
Change-Id: I4f2f768738d0f53fec28ed3f8e8f577cbc13431e
Reported-by: Andreas Beckmann <anbe@debian.org>

kernel-module/common_stats.h

@@ -4,8 +4,11 @@
 
 #ifdef __KERNEL__
 typedef atomic64_t atomic64;
+#if LINUX_VERSION_CODE >= KERNEL_VERSION(5,1,0)
 static_assert(sizeof(atomic64_t) == sizeof(int64_t), "atomic64_t != int64_t");
 static_assert(sizeof(atomic_t) == sizeof(int), "atomic_t != int");
+// else: hope for the best
+#endif
 #else
 typedef int atomic_t;
 #endif