ipmi: fix refcount leak in i_ipmi_request()

ipmi: fix refcount leak in i_ipmi_request()

When a caller provides a `supplied_recv` message to i_ipmi_request(),
the function increments the user's `nr_msgs` reference count. If an
error occurs later, the out_err cleanup path only frees the recv_msg
if the function allocated it itself (i.e., !supplied_recv). In the
supplied_recv case the cleanup is skipped, leaving the reference count
elevated. The caller ipmi_request_supply_msgs() does not release the
supplied_recv on error, so the reference is permanently leaked.

Fix this by explicitly reverting the reference count operations when a
supplied recv_msg with a valid user pointer is present in the error
path: decrement nr_msgs and drop the user's kref.

Cc: stable@vger.kernel.org
Fixes: b52da4054ee0 ("ipmi: Rework user message limit handling")
Signed-off-by: Wentao Liang <vulab@iscas.ac.cn>
Message-ID: <20260603120634.3758747-1-vulab@iscas.ac.cn>
Signed-off-by: Corey Minyard <corey@minyard.net>