net: hsr: remove WARN_ONCE() in send_hsr_supervision_frame()

In the Linux kernel, the following vulnerability has been resolved:

net: hsr: remove WARN_ONCE() in send_hsr_supervision_frame()

Syzkaller reported [1] hitting a warning after failing to allocate

resources for skb in hsr_init_skb(). Since a WARN_ONCE() call will

not help much in this case, it might be prudent to switch to

netdev_warn_once(). At the very least it will suppress syzkaller

reports such as [1].

Just in case, use netdev_warn_once() in send_prp_supervision_frame()

for similar reasons.

[1]

HSR: Could not send supervision frame

WARNING: CPU: 1 PID: 85 at net/hsr/hsr_device.c:294 send_hsr_supervision_frame+0x60a/0x810 net/hsr/hsr_device.c:294

RIP: 0010:send_hsr_supervision_frame+0x60a/0x810 net/hsr/hsr_device.c:294

...

Call Trace:

<IRQ>

hsr_announce+0x114/0x370 net/hsr/hsr_device.c:382

call_timer_fn+0x193/0x590 kernel/time/timer.c:1700

expire_timers kernel/time/timer.c:1751 [inline]

__run_timers+0x764/0xb20 kernel/time/timer.c:2022

run_timer_softirq+0x58/0xd0 kernel/time/timer.c:2035

__do_softirq+0x21a/0x8de kernel/softirq.c:553

invoke_softirq kernel/softirq.c:427 [inline]

__irq_exit_rcu kernel/softirq.c:632 [inline]

irq_exit_rcu+0xb7/0x120 kernel/softirq.c:644

sysvec_apic_timer_interrupt+0x95/0xb0 arch/x86/kernel/apic/apic.c:1076

</IRQ>

<TASK>

asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:649

...

This issue is also found in older kernels (at least up to 5.10).