dccp: catch failed request_module call in dccp_probe init

Check the return value of request_module during dccp_probe initialisation,
bail out if that call fails.

Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Signed-off-by: Wang Weidong <wangweidong1@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>