[POWERPC] axonram: Do not delete gendisks queue in error path

On exit do not delete gendisk's queue because this is already done by
del_gendisk(). Doing it twice may cause memory damage.

Signed-off-by: Maximilian <maxim@de.ibm.com>
Signed-off-by: Arnd Bergmann <arnd.bergmann@de.ibm.com>
Signed-off-by: Paul Mackerras <paulus@samba.org>