at86rf230: fix lockdep splats

at86rf230: fix lockdep splats

This patch fix a lockdep in the at86rf230 driver, otherwise we get:

[   30.206517] =================================
[   30.211078] [ INFO: inconsistent lock state ]
[   30.215647] 3.14.0-20140108-1-00994-g32e9426 #163 Not tainted
[   30.221660] ---------------------------------
[   30.226222] inconsistent {HARDIRQ-ON-W} -> {IN-HARDIRQ-W} usage.
[   30.232514] systemd-udevd/157 [HC1[1]:SC0[0]:HE0:SE1] takes:
[   30.238439]  (&(&lp->lock)->rlock){?.+...}, at: [<c03600f8>] at86rf230_isr+0x18/0x44
[   30.246621] {HARDIRQ-ON-W} state was registered at:
[   30.251728]   [<c0061ce4>] __lock_acquire+0x7a4/0x18d8
[   30.257135]   [<c0063500>] lock_acquire+0x68/0x7c
[   30.262071]   [<c0588820>] _raw_spin_lock+0x28/0x38
[   30.267203]   [<c0361240>] at86rf230_xmit+0x1c/0x144
[   30.272412]   [<c057ba6c>] mac802154_xmit_worker+0x88/0x148
[   30.278271]   [<c0047844>] process_one_work+0x274/0x404
[   30.283761]   [<c00484c0>] worker_thread+0x228/0x374
[   30.288971]   [<c004cfb8>] kthread+0xd0/0xe4
[   30.293455]   [<c000dac8>] ret_from_fork+0x14/0x2c
[   30.298493] irq event stamp: 8948
[   30.301963] hardirqs last  enabled at (8947): [<c00cb290>] __kmalloc+0xb4/0x110
[   30.309636] hardirqs last disabled at (8948): [<c00115d4>] __irq_svc+0x34/0x5c
[   30.317215] softirqs last  enabled at (8452): [<c0037324>] __do_softirq+0x1dc/0x264
[   30.325243] softirqs last disabled at (8439): [<c0037638>] irq_exit+0x80/0xf4

We use the lp->lock inside the isr of at86rf230, that's why we need the
irqsave spinlock calls.

Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>