dasd: fix list_del corruption during format

If I/O errors occur during format a kernel panic with a list_del
corruption may occur.

Stop error recovery procedure after an erp action was taken.

Signed-off-by: Stefan Haberland <stefan.haberland@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>