RDMA/bnxt_re: Fix uninitialized struct bit field rsvd1

The bit field rsvd1 in resp is not being initialized and garbage data is
being copied from the stack back to userspace via the ib_copy_to_udata
call. Fix this by setting the entire struct resp to zero; this will ensure
that further new bit fields in the future will be zero'd too.

Link: https://lore.kernel.org/r/20210623182437.163801-1-colin.king@canonical.com
Addresses-Coverity: ("Uninitialized scalar variable")
Fixes: 87974051

 ("RDMA/bnxt_re: Update ABI to pass wqe-mode to user space")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
[jgg: remove extra zeroing]
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>