cfg80211: permanently disable channels specified by base settings

if a custom regulatory domain is passed and if a rule for a channel
indicates it should be disabled that channel should always remain
disabled as per its documentation and design.
Likewise if WIPHY_FLAG_STRICT_REGULATORY flag is set and a
regulatory_hint() is issued if a channel is disabled that channel should
remain disabled.
Without this change only drivers that set the _orig flags appropriately
on their own would ensure disallowed channels remaind disabled. This
helps drivers save code by relying on the APIS provided to entrust
channels that should not be enabled be respected by only having to use
wiphy_apply_custom_regulatory() or regulatory_hint() with the
WIPHY_FLAG_STRICT_REGULATORY set.
If wiphy_apply_custom_regulatory() is used together with
WIPHY_FLAG_STRICT_REGULATORY and a regulatory_hint() issued later, the
incoming regulatory domain can override previously set _orig parameters
from the initial custom regulatory setting.

Change-Id: Ia1af4b293bd299ac20e1934e5e03e633ecb9d6ee
Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
Signed-off-by: Mihir Shete <smihir@codeaurora.org>