qlnxe: Refactor setting the promiscuous and allmulti mode

There are two entry points to set the promiscuous and allmulti mode.
One is ioctl, and another is the init routine. Given they share almost
the identical logic, refactor a little to make the code more clear.

While here, for the ioctl, translate the error to EINVAL to avoid
confusing the net stack.

Reviewed by: kbowling
MFC after: 5 days
Differential Revision: https://reviews.freebsd.org/D54890