ice: remove dead code

The check for a NULL pf pointer is moot since the earlier declaration and
assignment of struct device *dev already de-referenced the pointer.  Also,
the only caller of ice_set_dflt_mib() already ensures pf is not NULL.

Cc: Dave Ertman <david.m.ertman@intel.com>
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Bruce Allan <bruce.w.allan@intel.com>
Tested-by: Tony Brelinski <tonyx.brelinski@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>