rawdev: add private data size to info query

rawdev: add private data size to info query

Currently with the rawdev API there is no way to check that the structure
passed in via the dev_private pointer in the dev_info structure is of the
correct type - it's just checked that it is non-NULL. Adding in the length
of the expected structure provides a measure of typechecking, and can also
be used for ABI compatibility in future, since ABI changes involving
structs almost always involve a change in size.

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Reviewed-by: Rosen Xu <rosen.xu@intel.com>
Acked-by: Rosen Xu <rosen.xu@intel.com>
Acked-by: Nipun Gupta <nipun.gupta@nxp.com>