Two rules with different values of suppress_prefix or suppress_ifgroup
are not the same. This fixes an -EEXIST when running:

   $ ip -4 rule add table main suppress_prefixlength 0
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Fixes: f9d4b0c1 ("fib_rules: move common handling of newrule delrule msgs into fib_nl2rule")
Signed-off-by: David S. Miller <davem@davemloft.net>