ipmi: remove IPMI_CHECK_RESERVATION() macro

Some IPMI command handlers in the BMC simulator use a macro
IPMI_CHECK_RESERVATION() to check a SDR reservation but the macro
implicitly uses local variables. This patch simply removes it.

Signed-off-by: Cédric Le Goater <clg@fr.ibm.com>
Acked-by: Corey Minyard <cminyard@mvista.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
