net: macb: add TX stall timeout callback to recover from lost TSTART write

net: macb: add TX stall timeout callback to recover from lost TSTART write

The MACB found in the Raspberry Pi RP1 suffers from sporadic stalls on
the TX queue.
While the exact root cause is not yet fully understood, it is likely
related to a hardware issue where a TSTART write to the NCR register
is missed, preventing the transmission from being kicked off.

Implement a timeout callback to handle TX queue stalls, triggering the
existing restart mechanism to recover.

Link: https://lore.kernel.org/all/20260514215459.36109-1-lukasz@raczylo.com/
Fixes: dc110d1b23564 ("net: cadence: macb: Add support for Raspberry Pi RP1 ethernet controller")
Signed-off-by: Lukasz Raczylo <lukasz@raczylo.com>
Co-developed-by: Steffen Jaeckel <sjaeckel@suse.de>
Signed-off-by: Steffen Jaeckel <sjaeckel@suse.de>
Co-developed-by: Andrea della Porta <andrea.porta@suse.com>
Signed-off-by: Andrea della Porta <andrea.porta@suse.com>
Reviewed-by: Nicolai Buchwitz <nb@tipi-net.de>
Reviewed-by: Théo Lebrun <theo.lebrun@bootlin.com>
Link: https://patch.msgid.link/468f480454a314303bac6a54780b153f689f2267.1781598350.git.andrea.porta@suse.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>