net: bcmasp: fix memory leak when bringing down interface

When bringing down the TX rings we flush the rings but forget to
reclaimed the flushed packets. This leads to a memory leak since we
do not free the dma mapped buffers. This also leads to tx control
block corruption when bringing down the interface for power
management.

Fixes: 490cb412

 ("net: bcmasp: Add support for ASP2.0 Ethernet controller")
Signed-off-by: Justin Chen <justin.chen@broadcom.com>
Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://lore.kernel.org/r/20240418180541.2271719-1-justin.chen@broadcom.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>