AA: generic: ar8216: add missing locking calls

AA: generic: ar8216: add missing locking calls

Backport of r34281.

Fixes the following lockdep warning:

[   19.160000] ------------[ cut here ]------------
[   19.160000] WARNING: at drivers/net/phy/ar8216.c:322 ar8216_rmw+0x54/0xa4()
[   19.170000] Modules linked in: nf_defrag_ipv4 nf_conntrack ehci_hcd
sd_mod pppox ipt_REJECT xt_TCPMSS ipt_LOG xt_comment xt_multip
ort xt_mac xt_limit iptable_mangle iptable_filter ip_tables xt_tcpudp
x_tables ppp_async ppp_generic slhc ath9k(O) ath9k_common(O) at
h9k_hw(O) ath(O) mac80211(O) usbcore usb_common scsi_mod nls_base crc7
crc_itu_t crc_ccitt cfg80211(O) compat(O) arc4 aes_generic cry
pto_blkcipher cryptomgr aead crypto_hash crypto_algapi ledtrig_timer
ledtrig_default_on leds_gpio gpio_button_hotplug(O)
[   19.210000] Call Trace:
[   19.220000] [<8028dc38>] dump_stack+0x8/0x34
[   19.220000] [<80072da0>] warn_slowpath_common+0x78/0xa4
[   19.230000] [<80072de4>] warn_slowpath_null+0x18/0x24
[   19.230000] [<801de820>] ar8216_rmw+0x54/0xa4
[   19.240000] [<801df460>] ar8216_mib_capture+0x70/0xd0
[   19.240000] [<801df944>] ar8xxx_mib_work_func+0x34/0x98
[   19.250000] [<80089a7c>] process_one_work+0x28c/0x460
[   19.250000] [<8008a630>] worker_thread+0x22c/0x334
[   19.260000] [<8008e544>] kthread+0x88/0x90
[   19.260000] [<80065020>] kernel_thread_helper+0x10/0x18
[   19.270000]
[   19.270000] ---[ end trace 22e9d696adfa6a08 ]---

Signed-off-by: Gabor Juhos <juhosg@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@34369 3c298f89-4303-0410-b956-a3cf2f4a3e73