selinux: Fix error return code in sel_ib_pkey_sid_slow()

selinux: Fix error return code in sel_ib_pkey_sid_slow()

BugLink: https://bugs.launchpad.net/bugs/1905618
commit c350f8bea271782e2733419bd2ab9bf4ec2051ef upstream.

Fix to return a negative error code from the error handling case
instead of 0 in function sel_ib_pkey_sid_slow(), as done elsewhere
in this function.

Cc: stable@vger.kernel.org
Fixes: 409dcf31538a ("selinux: Add a cache for quicker retreival of PKey SIDs")
Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: Chen Zhou <chenzhou10@huawei.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>