ipmi: fix statistics counting issues

Bela Lubkin noticed that the statistics for send IPMB and LAN commands
in the IPMI driver could be incremented even if an error occurred.  Move
the increments to the proper place to avoid this.

Also add some statistics for retransmissions that failed, and some little
helper functions to neaten up the code a little.

Signed-off-by: Corey Minyard <cminyard@mvista.com>
Cc: Bela Lubkin <blubkin@vmware.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>