net/smc: use __aligned_u64 for 64-bit smc_diag fields

Commit 4b1b7d3b ("net/smc: add SMC-D diag support") introduced
new UAPI-exposed structure, struct smcd_diag_dmbinfo.  However,
it's not usable by compat binaries, as it has different layout there.
Probably, the most straightforward fix that will avoid similar issues
in the future is to use __aligned_u64 for 64-bit fields.

Fixes: 4b1b7d3b ("net/smc: add SMC-D diag support")
Signed-off-by: Eugene Syromiatnikov <esyr@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>