igb: rename igb_update_mc_addr_list_82575 to not include the 82575

There isn't much point in having the _82575 hanging off the end of this
function since there aren't any other version of this function running
around within this driver.  This also allows for a bit of whitespace
cleanup due to a shorter function name.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>