In case of sp2 pci driver registration fail, fix the error path to
start with sp1 pci driver unregister.

Fixes: c3ab4354 ("mlxsw: spectrum: Extend to support Spectrum-2 ASIC")
Signed-off-by: NJiri Pirko <jiri@mellanox.com>
Signed-off-by: NIdo Schimmel <idosch@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>