dmaengine: bcm2835: do not call vchan_vdesc_fini() with lock held

vchan_vdesc_fini() can't be called locked. Instead, call
vchan_terminate_vdesc() which delays the freeing of the descriptor to
vchan_synchronize().

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
Link: https://lore.kernel.org/r/20191216105328.15198-2-s.hauer@pengutronix.de


Signed-off-by: Vinod Koul <vkoul@kernel.org>