net: fib: fix incorrect call_rcu_bh()

After IP route cache removal, I believe rcu_bh() has very little use and
we should remove this RCU variant, since it adds some cycles in fast
path.
Anyway, the call_rcu_bh() use in fib_true is obviously wrong, since
some users only assert rcu_read_lock().

4619.617291:   <0> Internal error: Oops: 5 [#1] PREEMPT SMP ARM
114619.622541:   <4> Modules linked in: wlan(O) adsprpc [last unloaded: wlan]
114619.628980:   <4> CPU: 1    Tainted: G        W  O  (3.4.0-g366f2d7-00028-gde45140 #1)
114619.636427:   <4> PC is at leaf_walk_rcu+0x50/0x9c
114619.640761:   <4> LR is at fib_route_seq_next+0x58/0x7c
...[ Dmesg snip snip ]...
14620.187747:   <0> 5fe0: 405a3cd4 405a3ca0 007207ac 0071c098 80000010 00000012 00000000 00000000
114620.196018:   <4> [<c0720ec4>] (leaf_walk_rcu+0x50/0x9c) from [<c07210b0>] (fib_route_seq_next+0x58/0x7c)
114620.205114:   <4> [<c07210b0>] (fib_route_seq_next+0x58/0x7c) from [<c01642d8>] (seq_read+0x304/0x498)
114620.213964:   <4> [<c01642d8>] (seq_read+0x304/0x498) from [<c018daf8>] (proc_reg_read+0x80/0x98)
114620.222388:   <4> [<c018daf8>] (proc_reg_read+0x80/0x98) from [<c0147e90>] (vfs_read+0xa4/0x12c)
114620.230720:   <4> [<c0147e90>] (vfs_read+0xa4/0x12c) from [<c0147f4c>] (sys_read+0x34/0x68)
114620.238625:   <4> [<c0147f4c>] (sys_read+0x34/0x68) from [<c000e2e0>] (ret_fast_syscall+0x0/0x30)

CRs-Fixed: 614067

Change-Id: If493d4873de2ab5fa17e54b451871b4b3d469865
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Git-commit: 0c03eca3
Git-repo: https://www.codeaurora.org/cgit/quic/la/kernel/msm-3.10


Signed-off-by: Vijaya Kumar T M <vtmuni@codeaurora.org>