hw/arm/exynos4210: Connect serial port DMA busy signals with pl330

hw/arm/exynos4210: Connect serial port DMA busy signals with pl330

The Exynos4210 serial driver uses an interrupt line to signal if receive
data is available. Connect that interrupt with the DMA controller's
'peripheral busy' gpio pin to stop the DMA if there is no more receive
data available. Without this patch, receive DMA runs wild and fills the
entire receive DMA buffer with invalid data.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Message-id: 20200123052540.6132-9-linux@roeck-us.net
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>