ath9k: Fix bug in starting ani

There are few places where ANI is started without checking
if it is right to start. This might lead to a case where ani
timer would be left undeleted and cause improper memory acccess
during module unload. This bug is clearly exposed with
paprd support where the driver detects tx hang and does a
chip reset. During this reset ani is (re)started without checking
if it needs to be started. This would leave a timer scheduled
even after all the resources are freed and cause a panic.

This patch introduces a bit in sc_flags to indicate if ani
needs to be started in sw_scan_start() and ath_reset().
This would fix the following panic. This issue is easily seen
with ar9003 + paprd.

 BUG: unable to handle kernel paging request at 0000000000003f38
[<ffffffff81075391>] ? __queue_work+0x41/0x50
[<ffffffff8106afaa>] run_timer_softirq+0x17a/0x370
[<ffffffff81088be8>] ? tick_dev_program_event+0x48/0x110
[<ffffffff81061f69>] __do_softirq+0xb9/0x1f0
[<ffffffff810ba060>] ? handle_IRQ_event+0x50/0x160
[<ffffffff8100af5c>] call_softirq+0x1c/0x30
[<ffffffff8100c9f5>] do_softirq+0x65/0xa0
[<ffffffff81061e25>] irq_exit+0x85/0x90
[<ffffffff8155e095>] do_IRQ+0x75/0xf0
[<ffffffff815570d3>] ret_from_intr+0x0/0x11
<EOI>
[<ffffffff812fd67b>] ? acpi_idle_enter_simple+0xe4/0x119
[<ffffffff812fd674>] ? acpi_idle_enter_simple+0xdd/0x119
[<ffffffff81441c87>] cpuidle_idle_call+0xa7/0x140
[<ffffffff81008da3>] cpu_idle+0xb3/0x110
[<ffffffff81550722>] start_secondary+0x1ee/0x1f5

Signed-off-by: Vasanthakumar Thiagarajan <vasanth@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>