ieee802154: ieee802154_cc13xx_cc26xx_subg: Fix tcp timeout

- If status == PROP_ERROR_RXBUF, that means rx buffer head is not empty.
  In case of this, RF_EventRxEntryDone is never triggered and thus we
  enter an infinite loop of nothing happening. Due to this, TCP socket
  times out.
- To fix this, we need to free rx buffer current head. However, it seems
  better to free all the elements that are already finished instead of
  just head.
- Before 128354ae, the buffer was reset
  every time drv_rx_start was called. However, that also seems wrong for
  a ring buffer. So I am freeing the finished buffers instead.
- Tested on Beagleconnect Freedom.
- Fixes https://github.com/zephyrproject-rtos/zephyr/issues/71191



Signed-off-by: Ayush Singh <ayushdevel1325@gmail.com>