brcm80211: smac: don't validate channels against internal regulatory data

The core regulatory support will disable channels not allowed by
regulatory rules, so brcmsmac doesn't need to check whether or not the
requested channel is permitted by regulatory.
Reviewed-by: Arend Van Spriel <arend@broadcom.com>
Reviewed-by: Pieter-Paul Giesberts <pieterpg@broadcom.com>
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>