serial: 8250: 8250_omap.c: Clear DMA RX running status only after DMA termination...

serial: 8250: 8250_omap.c: Clear DMA RX running status only after DMA termination is done

Clear rx_running flag only after DMA teardown polling completes. In the
previous implementation the flag was being cleared while hardware teardown
was still in progress, creating a mismatch between software state
(flag = 0, "ready") and hardware state (still terminating).

Signed-off-by: Moteen Shah <m-shah@ti.com>
Link: https://patch.msgid.link/20260112081829.63049-3-m-shah@ti.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>