ipmi: bail out if init_srcu_struct fails

In case, init_srcu_struct fails (because of memory allocation failure), we
might proceed with the driver initialization despite srcu_struct not being
entirely initialized.

Fixes: 913a89f0 ("ipmi: Don't initialize anything in the core until something uses it")
Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Cc: Corey Minyard <cminyard@mvista.com>
Cc: stable@vger.kernel.org
Message-Id: <20211217154410.1228673-1-cascardo@canonical.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>