dmaengine: amba-pl08x: make filter check that the channel is owned by pl08x

Before converting the dma channel to our private data structure, first
check that the channel is indeed one which our driver registered.  We
do this by ensuring that the underlying device is bound to our driver.

This avoids potential oopses if we try to reference 'plchan->name'
against a foreign drivers dma channel.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>