dmaengine: PL08x: use vchan's spinlock

Initialize the vchan struct, and use the provided spinlock rather than
our own.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Tested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/drivers/dma/Kconfig b/drivers/dma/Kconfig
index eb2b60e..be0dc3b 100644
--- a/drivers/dma/Kconfig
+++ b/drivers/dma/Kconfig
@@ -53,6 +53,7 @@
 	bool "ARM PrimeCell PL080 or PL081 support"
 	depends on ARM_AMBA && EXPERIMENTAL
 	select DMA_ENGINE
+	select DMA_VIRTUAL_CHANNELS
 	help
 	  Platform has a PL08x DMAC device
 	  which can provide DMA engine support