Switch to Packed vs Aligned mlx5 WQE ctrl (#542)

Summary:
Pull Request resolved: #542

Fix bug in alignment, C definition is:
  struct mlx5_wqe_ctrl_seg {
	__be32		opmod_idx_opcode;
	__be32		qpn_ds;
	uint8_t		signature;
	__be16		dci_stream_channel_id;
	uint8_t		fm_ce_se;
	__be32		imm;
  } __attribute__((__packed__)) __attribute__((__aligned__(4)));

LSS: we want to use packed / packed(1) with binding (drop align, works fine).

Reviewed By: allenwang28

Differential Revision: D78362878

fbshipit-source-id: e6a4deff1b9108403258ab573a51a9d5fbc7ca3f

Author: dstaay-fb

rdmacore-sys/src/lib.rs

@@ -9,7 +9,7 @@
 // sections of code adapted from https://github.com/jonhoo/rust-ibverbs
 // Copyright (c) 2016 Jon Gjengset under MIT License (MIT)
 
-#[repr(C, align(4))]
+#[repr(C, packed(1))]
 #[derive(Debug, Default, Clone, Copy)]
 pub struct mlx5_wqe_ctrl_seg {
     pub opmod_idx_opcode: u32,