The lan966x is using the function 'packing' to create/extract the
information for the IFH, that is used to be added in front of the frames
when they are injected/extracted.
Therefore update the Kconfig to select config option 'PACKING' whenever
lan966x driver is enabled.

Fixes: db8bcaad ("net: lan966x: add the basic lan966x driver")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Horatiu Vultur <horatiu.vultur@microchip.com>
Signed-off-by: David S. Miller <davem@davemloft.net>