[next-20190530] Boot failure on PowerPC

[Sachin Sant]

Latest next fails to boot with a kernel panic on POWER9.

[   33.689332] Kernel panic - not syncing: stack-protector: Kernel stack is corrupted in: write_irq_affinity.isra.5+0x15c/0x160
[   33.689346] CPU: 35 PID: 4907 Comm: irqbalance Not tainted 5.2.0-rc2-next-20190530-autotest-autotest #1
[   33.689352] Call Trace:
[   33.689356] [c0000018d974bab0] [c000000000b5328c] dump_stack+0xb0/0xf4 (unreliable)
[   33.689364] [c0000018d974baf0] [c000000000120694] panic+0x16c/0x408
[   33.689370] [c0000018d974bb80] [c00000000012010c] __stack_chk_fail+0x2c/0x30
[   33.689376] [c0000018d974bbe0] [c0000000001b859c] write_irq_affinity.isra.5+0x15c/0x160
[   33.689383] [c0000018d974bd30] [c0000000004d6f30] proc_reg_write+0x90/0x110
[   33.689388] [c0000018d974bd60] [c00000000041453c] __vfs_write+0x3c/0x70
[   33.689394] [c0000018d974bd80] [c000000000418650] vfs_write+0xd0/0x250
[   33.689399] [c0000018d974bdd0] [c000000000418a2c] ksys_write+0x7c/0x130
[   33.689405] [c0000018d974be20] [c00000000000b688] system_call+0x5c/0x70

Machine boots till login prompt and then panics few seconds later.

Last known next build was May 24th. Will attempt few builds till May 30 to
narrow down this problem.

Thanks
-Sachin