ipmi: remove redundant initialization of bmc

The pointer bmc is being initialized and this initialized value is
never being read, so this is assignment redundant and can be removed.
Cleans up clang warning:

warning: Value stored to 'bmc' during its initialization is never read

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Corey Minyard <cminyard@mvista.com>