[PATCH] IPMI: fix issues reported by Coverity in ipmi_msghandler.c

While looking to the report by Coverity in ipmi, I came across the
following issue:

The IPMI message handler relies on two defines which are the same -one in
include/linux/ipmi.h
#define IPMI_NUM_CHANNELS 0x10
and one in drivers/char/ipmi/ipmi_msghandler.
#define IPMI_MAX_CHANNELS       16
These are used interchangeably in ipmi_msghandler.c, but since the array
addr->channels[] is of size IPMI_MAX_CHANNELS, I have made a patch that
uses IPMI_MAX_CHANNELS for all the checks for the array index.

NOTE: You could probably remove the line that defines IPMI_NUM_CHANNELS
from ipmi.h, or move IPMI_MAX_CHANNELS to ipmi.h

Signed-off-by: Jayachandran C. <c.jayachandran@gmail.com>
Cc: Corey Minyard <minyard@acm.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>