staging: r8188eu: Remove union wrapping of recv_frame

We have now removed everthing from the union except the struct. The union
can be deleted, the struct renamed, and the referencing of members of the
struct becomes a lot simpler.

Some, but not all, of the problems noted by checkpatch.pl have been fixed.

Sugggested-by: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Cc: Jes Sorensen <Jes.Sorensen@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>