net/smsc911x: Add regulator support

net/smsc911x: Add regulator support

Add some basic regulator support for the power pins, as needed
by the ST-Ericsson Snowball platform that powers up the SMSC911
chip using an external regulator.

Platforms that use regulators and the smsc911x and have no defined
regulator for the smsc911x and claim complete regulator
constraints with no dummy regulators will need to provide it, for
example using a fixed voltage regulator. It appears that this may
affect (apart from Ux500 Snowball) possibly these archs/machines
that from some grep:s appear to define both CONFIG_SMSC911X and
CONFIG_REGULATOR:

- ARM Freescale mx3 and OMAP 2 plus, Raumfeld machines
- Blackfin
- Super-H

Cc: Paul Mundt <[email protected]>
Cc: [email protected]
Cc: Sascha Hauer <[email protected]>
Cc: Tony Lindgren <[email protected]>
Cc: [email protected]
Cc: Mike Frysinger <[email protected]>
Cc: [email protected]
Reviewed-by: Mark Brown <[email protected]>
Signed-off-by: Robert Marklund <[email protected]>
Signed-off-by: Linus Walleij <[email protected]>
Signed-off-by: David S. Miller <[email protected]>