brcmfmac: add support to move wiphy instance into network namespace

To support network namespace the driver must assure all created
network interfaces are in the same namespace as the wiphy instance
and flag the support using WIPHY_FLAG_NETNS_OK.

Verified using two terminals:

 Terminal 1			Terminal 2
 --------------------------	---------------------------------
 # ip netns add brcm-wifi	# iw dev
				phy#0
					Interface wlan3
						ifindex 11
						wdev 0x1
 # ip netns exec brcm-wifi bash
 # iw dev
 # echo $$
 20337			# iw phy0 set netns 20337
 # iw dev
 phy#0
	Interface wlan3
		ifindex 11
		wdev 0x2
 # iw phy0 interface add wl3.ap type __ap
 # iw dev
 phy#0
	Interface wl3.ap
		ifindex 2
		wdev 0x3
	Interface wlan3
		ifindex 11
		wdev 0x2
				# iw dev
 # iw phy0 set netns 1
 # iw dev
				# iw dev
				phy#0
					Interface wl3.ap
						ifindex 2
						wdev 0x5
					Interface wlan3
						ifindex 11
						wdev 0x4

Note:
	increasing wdev identifier above indicates issue in
	cfg80211 which is addressed separately.

Tested-by: Mark Asselstine <mark.asselstine@windriver.com>
Signed-off-by: Arend van Spriel <arend.vanspriel@broadcom.com>
Reviewed-by: Franky Lin <franky.lin@broadcom.com>
Reviewed-by: Hante Meuleman <hante.meuleman@broadcom.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>