ARM: da8xx: use platform data for CFGCHIP syscon regmap

This converts from using a platform device for the CFGCHIP syscon
regmap to using platform data to pass the regmap to consumers.

A lazy getter function is used so that the regmap will only be
created if it is actually used. This function will also be used
in the clock init when we convert to the common clock framework.

The USB PHY driver is currently the only consumer. This driver is
updated to use platform data to get the CFGCHIP regmap instead of
syscon_regmap_lookup_by_pdevname().

Signed-off-by: David Lechner <david@lechnology.com>
Acked-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Sekhar Nori <nsekhar@ti.com>