RDMA/amso1100: Fix a NULL dereference in error path

This patch fixes a NULL dereference spotted by the Coverity checker.

Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Acked-by: Steve Wise <swise@opengridcomputing.com>
Acked-by: Tom Tucker <tom@opengridcomputing.com>
Signed-off-by: Roland Dreier <rolandd@cisco.com>