igb_uio: cast private data to correct struct type

igb_uio: cast private data to correct struct type

This was working fine because addresses of two structs are same:

struct A {
	struct B b;
} a;

As above sample "a" and "b" has same address.

Now casting private data back to the correct struct type, to the one
stored.

Fixes: af75078fece3 ("first public release")

Signed-off-by: Ferruh Yigit <ferruh.yigit@intel.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>