iwlwifi: pcie: disable BHs in iwl_pcie_txq_check_wrptrs

iwlwifi: pcie: disable BHs in iwl_pcie_txq_check_wrptrs

This fixes:

=================================
[ INFO: inconsistent lock state ]
3.14.3+ #5 Tainted: G           O
---------------------------------
inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
swapper/3/0 [HC0[0]:SC1[3]:HE1:SE0] takes:
 (&(&txq->lock)->rlock){+.?...}, at: [<ffffffffa059803c>] iwl_pcie_enqueue_hcmd+0x12c/0x1000 [iwlwifi]
{SOFTIRQ-ON-W} state was registered at:
  [<ffffffff810d9071>] __lock_acquire+0x5f1/0x13b0
  [<ffffffff810d9ee0>] lock_acquire+0xb0/0x1f0
  [<ffffffff817ef80e>] _raw_spin_lock+0x3e/0x80
  [<ffffffffa0598f7a>] iwl_pcie_txq_check_wrptrs+0x6a/0xb0 [iwlwifi]
  [<ffffffffa0594b5a>] iwl_pcie_irq_handler+0xdba/0x2670 [iwlwifi]
  [<ffffffff810ef1e0>] irq_thread_fn+0x20/0x50
  [<ffffffff810ef77f>] irq_thread+0x11f/0x150
  [<ffffffff810a04f0>] kthread+0xf0/0x110
  [<ffffffff817fa4bc>] ret_from_fork+0x7c/0xb0
irq event stamp: 1142192
hardirqs last  enabled at (1142192): [<ffffffff817efb6c>] _raw_spin_unlock_irq+0x2c/0x40
hardirqs last disabled at (1142191): [<ffffffff817ef9ef>] _raw_spin_lock_irq+0x1f/0x80
softirqs last  enabled at (1142188): [<ffffffff81079082>] _local_bh_enable+0x22/0x50
softirqs last disabled at (1142189): [<ffffffff8107ad35>] irq_exit+0xe5/0xf0

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&(&txq->lock)->rlock);
  <Interrupt>
    lock(&(&txq->lock)->rlock);

Fixes: ea68f46070c7 ("iwlwifi: pcie: clarify TX queue need_update handling")
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>