hw/arm/exynos4210: Fix DMA initialization

hw/arm/exynos4210: Fix DMA initialization

First parameter to exynos4210_get_irq() is not the SPI port number,
but the interrupt group number. Interrupt groups are 20 for mdma
and 21 for pdma. Interrupts are not inverted. Controllers support 32
events (pdma) or 31 events (mdma). Events must all be routed to a single
interrupt line. Set other parameters as documented in Exynos4210 datasheet,
section 8 (DMA controller).

Fixes: 59520dc65e ("hw/arm/exynos4210: Add DMA support for the Exynos4210")
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Message-id: 20200123052540.6132-4-linux@roeck-us.net
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>