mmc: mvsdio: use devm_ API to simplify/correct error paths.

There are a number of bugs in the error paths of this driver.  Make
use of devm_ functions to simplify the cleanup on error.

Based on a patch by Russell King.

Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Jason Cooper <jason@lakedaemon.net>