Bluetooth: MGMT: Fix error report for ADD_EXT_ADV_PARAMS

When validating the parameter length for MGMT_OP_ADD_EXT_ADV_PARAMS
command, use the correct op code in error status report:
was MGMT_OP_ADD_ADVERTISING, changed to MGMT_OP_ADD_EXT_ADV_PARAMS.

Fixes: 12410572

 ("Bluetooth: Break add adv into two mgmt commands")
Signed-off-by: Inga Stotland <inga.stotland@intel.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>