Bluetooth: Replace zero-length array with flexible-array member

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://www.kernel.org/doc/html/v5.9-rc1/process/deprecated.html#zero-length-and-one-element-arraysSigned-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

net/bluetooth/msft.c

@@ -12,12 +12,13 @@
 struct msft_cp_read_supported_features {
 	__u8   sub_opcode;
 } __packed;
+
 struct msft_rp_read_supported_features {
 	__u8   status;
 	__u8   sub_opcode;
 	__le64 features;
 	__u8   evt_prefix_len;
-	__u8   evt_prefix[0];
+	__u8   evt_prefix[];
 } __packed;
 
 struct msft_data {