ipmi: replace goto by a return statement

Each routine using the IPMI_ADD_RSP_DATA, IPMI_CHECK_CMD_LEN or
IPMI_CHECK_RESERVATION macros needs to define a goto label 'out' to
handle hidden errors. Using directly a return statement has the same
effect and it removes the fact that 'out' needs to be defined.

The code exits in ipmi_sim_handle_command() are a little different
from the rest and a "possible" error in the macro IPMI_ADD_RSP_DATA is
handled before making use of it. This might be a bit excessive as a
minimum response len is currently 300 bytes and the patch checks that
at least 3 are available.

Signed-off-by: Cédric Le Goater <clg@fr.ibm.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Reviewed-by: Corey Minyard <cminyard@mvista.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
