staging: r8188eu: Remove get_recvframe_data()

This inline function checks that the pointer is not NULL and then returns
the rx_data member. Unfortunately, all 3 callers of this function have
dereferenced that pointer before this routine is called. As the check for
NULL is useless, eliminate the routine.

Reported-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>