ipmi: decrease the IPMI message transaction time in interrupt mode

Call the event handler immediately after starting the next message.

This change considerably decreases the IPMI transaction time (cuts off
~9ms for a single ipmitool transaction).

Signed-off-by: Srinivas_Gowda <srinivas_g_gowda@dell.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>