RDMA/irdma: Fix kernel stack leak in irdma_create_user_ah()

RDMA/irdma: Fix kernel stack leak in irdma_create_user_ah()

struct irdma_create_ah_resp {  // 8 bytes, no padding
    __u32 ah_id;               // offset 0 - SET (uresp.ah_id = ah->sc_ah.ah_info.ah_idx)
    __u8  rsvd[4];             // offset 4 - NEVER SET <- LEAK
};

rsvd[4]: 4 bytes of stack memory leaked unconditionally. Only ah_id is assigned before ib_respond_udata().

The reserved members of the structure were not zeroed.

Cc: stable@vger.kernel.org
Fixes: b48c24c2d710 ("RDMA/irdma: Implement device supported verb APIs")
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>
Link: https://patch.msgid.link/3-v1-83e918d69e73+a9-rdma_udata_rc_jgg@nvidia.com
Signed-off-by: Leon Romanovsky <leon@kernel.org>