RDMA/iwpm: Remove redundant initialization of pointer err_str

The pointer err_str is being initialized with a value that is never read,
it is being updated later on. The assignment is redundant and can be
removed.

Link: https://lore.kernel.org/r/[e-mail]
Addresses-Coverity: ("Unused value")
Signed-off-by: Colin Ian King <[e-mail]>
Signed-off-by: Jason Gunthorpe <[e-mail]>

drivers/infiniband/core/iwpm_util.c

···
 {
 	struct sk_buff *skb = NULL;
 	struct nlmsghdr *nlh;
-	const char *err_str = "";
+	const char *err_str;
 	int ret = -EINVAL;
 
 	skb = iwpm_create_nlmsg(RDMA_NL_IWPM_HELLO, &nlh, nl_client);