net: ps3_gelic_net: handle skb allocation failures

net: ps3_gelic_net: handle skb allocation failures

Handle skb allocation failures in RX path, to avoid NULL pointer
dereference and RX stalls under memory pressure. If the refill fails
with -ENOMEM, complete napi polling and wake up later to retry via timer.
Also explicitly re-enable RX DMA after oom, so the dmac doesn't remain
stopped in this situation.

Previously, memory pressure could lead to skb allocation failures and
subsequent Oops like:

	Oops: Kernel access of bad area, sig: 11 [#2]
	Hardware name: SonyPS3 Cell Broadband Engine 0x701000 PS3
	NIP [c0003d0000065900] gelic_net_poll+0x6c/0x2d0 [ps3_gelic] (unreliable)
	LR [c0003d00000659c4] gelic_net_poll+0x130/0x2d0 [ps3_gelic]
	Call Trace:
	  gelic_net_poll+0x130/0x2d0 [ps3_gelic] (unreliable)
	  __napi_poll+0x44/0x168
	  net_rx_action+0x178/0x290

Steps to reproduce the issue:
	1. Start a continuous network traffic, like scp of a 20GB file
	2. Inject failslab errors using the kernel fault injection:
	    echo -1 > /sys/kernel/debug/failslab/times
	    echo 30 > /sys/kernel/debug/failslab/interval
	    echo 100 > /sys/kernel/debug/failslab/probability
	3. After some time, traces start to appear, kernel Oopses
	   and the system stops

Step 2 is not always necessary, as it is usually already triggered by
the transfer of a big enough file.

Fixes: 02c1889166b4 ("ps3: gigabit ethernet driver for PS3, take3")
Signed-off-by: Florian Fuchs <fuchsfl@gmail.com>
Link: https://patch.msgid.link/20251113181000.3914980-1-fuchsfl@gmail.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>