Russell King suggested that felix_vsc9959, seville_vsc9953 and
ocelot_ext have a large portion of duplicated init code, which could be
made common [1].

[1]: https://lore.kernel.org/all/Zh1GvcOTXqb7CpQt@shell.armlinux.org.uk/

Here, we take the following common steps:
- "felix" and "ds" structure allocation
- "felix", "ocelot" and "ds" basic structure initialization
- dsa_register_switch() call

and we make a common function out of them.

For every driver except felix_vsc9959, this is also the entire probing
procedure. For felix_vsc9959, we also need to do some PCI-specific
stuff, which can easily be reordered to be done before, and unwound on
failure.

We also have to convert the bus-specific platform_set_drvdata() and
pci_set_drvdata() calls into dev_set_drvdata(). But this should have no
impact on the behavior.
Suggested-by: "Russell King (Oracle)" <linux@armlinux.org.uk>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Tested-by: Colin Foster <colin.foster@in-advantage.com>
Signed-off-by: David S. Miller <davem@davemloft.net>