UPSTREAM: net: dsa: setup master ethtool unconditionally

When a DSA switch tree is meant to be applied, it already has a CPU
port. Thus remove the condition of dst->cpu_dp.

Moreover, the next lines access dst->cpu_dp unconditionally.

Signed-off-by: Vivien Didelot <vivien.didelot@savoirfairelinux.com>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit cd8d7dd4
https://github.com/torvalds/linux.git

)
Signed-off-by: Khasim Syed Mohammed <khasim.mohammed@linaro.org>