net: fec: fix spin_lock dead lock
net: fec: fix spin_lock dead lock

=========================================================
[ INFO: possible irq lock inversion dependency detected ]
3.8.0-rc5+ #82 Not tainted
---------------------------------------------------------
swapper/0/0 just changed the state of lock:
 (&(&fep->hw_lock)->rlock){..-...}, at: [<8034e2f8>] fec_enet_start_xmit+0x48/0x                      2cc
but this lock took another, SOFTIRQ-unsafe lock in the past:
(prepare_lock){+.+.+.}

and interrupts could create inverse lock ordering between them.
other info that might help us debug this:
Possible interrupt unsafe locking scenario:

CPU0				CPU1
----				----
lock(prepare_lock);
				local_irq_disable()
				lock(&(&fep->hw_lock)->rlock);
				lock(prepare_lock);
<Interrupt>
lock(&(&fep->hw_lock)->rlock);

*** DEADLOCK ***

Signed-off-by: Frank Li <d9a81cb4fa8b4f356eefd38684e2f43f08dbec49@freescale.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas