mlxsw: spectrum: Fix error path in mlxsw_sp_module_init()

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: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>