iavf/iavf_main: actually log ->src mask when talking about it

This fixes a copy-paste issue where dev_err would log the dst mask even
though it is clearly talking about src.

Found by Linux Verification Center (linuxtesting.org) with the SVACE
static analysis tool.

Fixes: 0075fa0f ("i40evf: Add support to apply cloud filters")
Signed-off-by: Daniil Tatianin <d-tatianin@yandex-team.ru>
Reviewed-by: Michal Swiatkowski <michal.swiatkowski@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>