x86/mm: Get rid of VM_BUG_ON in switch_tlb_irqs_off()

x86/mm: Get rid of VM_BUG_ON in switch_tlb_irqs_off()

If we hit the VM_BUG_ON(), we're detecting a genuinely bad situation,
but we're very unlikely to get a useful call trace.

Make it a warning instead.

Signed-off-by: Andy Lutomirski <[email protected]>
Cc: Borislav Petkov <[email protected]>
Cc: Jiri Kosina <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Link: http://lkml.kernel.org/r/3b4e06bbb382ca54a93218407c93925ff5871546.1504847163.git.luto@kernel.org
Signed-off-by: Ingo Molnar <[email protected]>