fix boot probability crash

[wangjianxin-canaan]

PR描述:

fix boot probability crash

详细描述:

解决系统启动时低概率crash问题，crash信息类似如下：
[ 13.547009] k510-isp 92600000.isp1: k510isp_pipeline_set_stream:state(1)
[ 13.554160] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000
[ 13.563132] Oops [#1]
[ 13.565418] Modules linked in:
[ 13.568526] CPU: 1 PID: 166 Comm: v4l2_drm.out Not tainted 4.17.0 #6
[ 13.574928] sepc: 0000000000000000 ra : 0000000000000001 sp : ffffffe009d6d9d0
[ 13.582174] gp : ffffffe000a2c458 tp : ffffffe0099d1280 t0 : 0000000000000000
[ 13.589428] t1 : fffffffffffeffff t2 : 0000000000000000 s0 : ffffffe00a3e6330
[ 13.596677] s1 : ffffffe00a3e2010 a0 : 0000000000000000 a1 : 0000000000000002
[ 13.603908] a2 : ffffffe000a2d7ac a3 : 0000000000000000 a4 : ffffffffffffffff
[ 13.611135] a5 : 0000000000000000 a6 : ffffffd0045d0014 a7 : 0000000000000008
[ 13.618362] s2 : ffffffe00a3e0018 s3 : ffffffe00a3c9100 s4 : 0000000000000001
[ 13.625588] s5 : 0000000000000005 s6 : 0000000000000001 s7 : 0000000000000001
[ 13.632816] s8 : ffffffe009d6d9c0 s9 : ffffffe000df6000 s10: 0000000200000022
[ 13.640042] s11: ffffffe00a3e0018 t3 : 0000000000000000 t4 : 0000000000000000
[ 13.647268] t5 : 0000000000000000 t6 : 0000000000000001
[ 13.652584] sstatus: 0000000200000120 sbadaddr: 0000000000000000 scause: 000000000000000c
[ 13.660772] CPU: 1 PID: 166 Comm: v4l2_drm.out Not tainted 4.17.0 #6
[ 13.667128] Call Trace:
[ 13.669602] [] walk_stackframe+0x0/0xa4
[ 13.675012] [] show_stack+0x2c/0x38
[ 13.680073] [] dump_stack+0x64/0x80
[ 13.685133] [] die+0x70/0xf8
[ 13.689588] [] do_page_fault+0x24c/0x358
[ 13.695083] [] ret_from_exception+0x0/0xc
[ 13.700752] ---[ end trace 67e47d6cb31794e8 ]---
[ 13.705394] Kernel panic - not syncing: Fatal exception in interrupt

关联issue:

fix #420