rtase: Reset TX subqueue when clearing TX ring

rtase_tx_clear() clears the TX ring and resets the ring indexes.
However, the TX queue state and BQL accounting are not reset at
the same time.

This may leave __QUEUE_STATE_STACK_XOFF asserted after
rtase_sw_reset(), preventing new TX packets from being scheduled.

Reset the TX subqueue when clearing the TX ring so the TX queue
state and BQL accounting are restored together.

Fixes: 5a2a2f15244c ("rtase: Implement the rtase_down function")
Cc: stable@vger.kernel.org
Signed-off-by: Justin Lai <justinlai0215@realtek.com>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Link: https://patch.msgid.link/20260602114659.12335-1-justinlai0215@realtek.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>