ipmi: ipmi_devintf: compat_ioctl method fails to take ipmi_mutex

When a 32 bit version of ipmitool is used on a 64 bit kernel, the
ipmi_devintf code fails to correctly acquire ipmi_mutex.  This results in
incomplete data being retrieved in some cases, or other possible failures.
Add a wrapper around compat_ipmi_ioctl() to take ipmi_mutex to fix this.

Signed-off-by: Benjamin LaHaise <bcrl@kvack.org>
Signed-off-by: Corey Minyard <cminyard@mvista.com>
Cc: stable@vger.kernel.org
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>