mlxsw: spectrum_matchall: Perform priority checks earlier

Perform the priority check earlier in the function instead of repeating
it for every action. This fixes a bug that allowed matchall rules with
sample action to be added in front of flower rules on egress.

Fixes: 54d0e963

 ("mlxsw: spectrum_matchall: Add support for egress sampling")
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Signed-off-by: David S. Miller <davem@davemloft.net>