Move away from the deprecated API and return the shiny new ERRPTR where
useful.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>