ice: fix error code in ice_eswitch_attach()

Set the "err" variable on this error path.

Fixes: fff292b4 ("ice: add VF representors one by one")
Signed-off-by: Dan Carpenter <dan.carpenter@linaro.org>
Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Link: https://lore.kernel.org/r/e0349ee5-76e6-4ff4-812f-4aa0d3f76ae7@moroto.mountain


Signed-off-by: Jakub Kicinski <kuba@kernel.org>