crypto: atmel-ecc - Remove duplicated error reporting in .remove()

Returning an error value in an i2c remove callback results in an error
message being emitted by the i2c core, but otherwise it doesn't make a
difference. The device goes away anyhow and the devm cleanups are
called.

As atmel_ecc_remove() already emits an error message on failure and the
additional error message by the i2c core doesn't add any useful
information, change the return value to zero to suppress this message.

Also make the error message a bit more drastical because when the device
is still busy on remove, it's likely that it will access freed memory
soon.

This patch is a preparation for making i2c remove callbacks return void.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Reviewed-by: Tudor Ambarus <tudor.ambarus@microchip.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>