vrf: remove unnecessary duplicate check
vrf: remove unnecessary duplicate check

The upper/lower functions already check for duplicate slaves so no need
to do it again.

Signed-off-by: Nikolay Aleksandrov <262b42b771725e3ebec40395f2b058e593df7462@cumulusnetworks.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs