spi: omap3: Convert to driver model

spi: omap3: Convert to driver model

After this conversion the driver will able to support both dm and non-dm
and code is more extensible like we can remove the non-dm part simply
without touching anycode if all the boards which are using this driver
become dm driven.

Cc: Tom Rini <[email protected]>
Reviewed-by: Simon Glass <[email protected]>
Acked-by: Christophe Ricard <[email protected]>
Tested-by: Christophe Ricard <[email protected]>
Signed-off-by: Jagan Teki <[email protected]>
[Set priv->wordlen, Add Kconfig entry and file credit for dm conversion]
Signed-off-by: Christophe Ricard <[email protected]>