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

(cherry picked from commit 45b1718fadae7d56051ba04ef9d7a175a602a226)
(cherry picked from commit b8d2c1c367465506b66a1696483caec1d04b2ea0)