iplink: Validate minimum tx rate is less than maximum tx rate

iplink: Validate minimum tx rate is less than maximum tx rate

According to the documentation (man ip-link), the minimum TXRATE should
be always <= Maximum TXRATE, but commit f89a2a05ffa9 ("Add support to
configure SR-IOV VF minimum and maximum Tx rate through ip tool") didn't
enforce it.

Fixes: f89a2a05ffa9 ("Add support to configure SR-IOV VF minimum and maximum Tx rate through ip tool")
Cc: Sucheta Chakraborty <sucheta.chakraborty@qlogic.com>
Signed-off-by: Gal Pressman <galp@mellanox.com>
Reviewed-by: Eran Ben Elisha <eranbe@mellanox.com>
Reviewed-by: Leon Romanovsky <leonro@mellanox.com>