tifm: Replace zero-length array with flexible-array

There is a regular need in the kernel to provide a way to declare having a
dynamically sized set of trailing elements in a structure. Kernel code should
always use “flexible array members”[1] for these cases. The older style of
one-element or zero-length arrays should no longer be used[2].

[1] https://en.wikipedia.org/wiki/Flexible_array_member
[2] https://github.com/KSPP/linux/issues/21Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

include/linux/tifm.h

@@ -124,7 +124,7 @@ struct tifm_adapter {
 	int                 (*has_ms_pif)(struct tifm_adapter *fm,
 					  struct tifm_dev *sock);
 
-	struct tifm_dev     *sockets[0];
+	struct tifm_dev     *sockets[];
 };
 
 struct tifm_adapter *tifm_alloc_adapter(unsigned int num_sockets,