PPC: xnu kernel expects FLUSH to be cleared on STOP

otherwise it gets stuck in a loop
so clear it when unsetting run when flush is set

void
IODBDMAStop( volatile IODBDMAChannelRegisters *registers)
{

	IOSetDBDMAChannelControl( registers,
	IOClearDBDMAChannelControlBits( kdbdmaRun )
		| IOSetDBDMAChannelControlBits(  kdbdmaFlush ));

DBDMA: writel 0x0000000000000b00 <= 0xa0002000
DBDMA: channel 0x16 reg 0x0
DBDMA:     status 0x00002000

	while( IOGetDBDMAChannelStatus( registers) & (
			kdbdmaActive | kdbdmaFlush))
		eieio();

DBDMA: readl 0x0000000000000b04 => 0x00002000
DBDMA: channel 0x16 reg 0x1
DBDMA: readl 0x0000000000000b04 => 0x00002000
DBDMA: channel 0x16 reg 0x1
DBDMA: readl 0x0000000000000b04 => 0x00002000
DBDMA: channel 0x16 reg 0x1
DBDMA: readl 0x0000000000000b04 => 0x00002000
DBDMA: channel 0x16 reg 0x1
it continues to get printed

}

Signed-off-by: Amadeusz Sławiński <amade@asmblr.net>
[agraf: replace tabs with spaces]
Signed-off-by: Alexander Graf <agraf@suse.de>
