NLA_UNSPEC usage is restricted from kernel version 5.4 by adding
a strict check while validating the nla_policy. The advantage
of this is that types not specified in the policy will be
rejected.
Driver can give exception to NLA_UNSPEC by setting
strict_start_type in the policy of a vendor command to NLA_U8
or some greater value. But it's better to set the type to a
valid type so that kernel can validate.
So, use NLA_BINARY with valid length instead of NLA_UNSPEC.
Change-Id: If6d559a3aa7b8719a515e00e271e313c02f8135f
CRs-Fixed: 2692293
698272c0b7