ipmi_si: Utilize temporary variable to hold device pointer

Introduce a temporary variable to hold a device pointer.
It can be utilized in the ->probe() and save a bit of LOCs.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Message-Id: <20210402174334.13466-4-andriy.shevchenko@linux.intel.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>