Revert "net: ipv6/addrconf: clamp preferred_lft to the minimum required"

temp_prefered_lft - INTEGER

	Preferred lifetime (in seconds) for temporary addresses. If

	temp_prefered_lft is less than the minimum required lifetime (typically

	5 seconds), the preferred lifetime is the minimum required. If

	5 seconds), temporary addresses will not be created. If

	temp_prefered_lft is greater than temp_valid_lft, the preferred lifetime

	is temp_valid_lft.

	write_unlock_bh(&idev->lock);

	/* From RFC 4941:

	 *

	 *     A temporary address is created only if this calculated Preferred

	 *     Lifetime is greater than REGEN_ADVANCE time units.  In

	 *     particular, an implementation must not create a temporary address

	 *     with a zero Preferred Lifetime.

	 *

	 * Clamp the preferred lifetime to a minimum of regen_advance, unless

	 * that would exceed valid_lft.

	 *

	/* A temporary address is created only if this calculated Preferred

	 * Lifetime is greater than REGEN_ADVANCE time units.  In particular,

	 * an implementation must not create a temporary address with a zero

	 * Preferred Lifetime.

	 * Use age calculation as in addrconf_verify to avoid unnecessary

	 * temporary addresses being generated.

	 */

	age = (now - tmp_tstamp + ADDRCONF_TIMER_FUZZ_MINUS) / HZ;

	if (cfg.preferred_lft <= regen_advance + age)

		cfg.preferred_lft = regen_advance + age + 1;

	if (cfg.preferred_lft > cfg.valid_lft) {

	if (cfg.preferred_lft <= regen_advance + age) {

		in6_ifa_put(ifp);

		in6_dev_put(idev);

		ret = -1;