DMA legacy is REQUIRED! wtf. unbreak 4.x on rpi2

target/arm/kernel/raspberry-pi2

@@ -6,6 +6,7 @@ CONFIG_HAVE_ARM_ARCH_TIMER=y
 CONFIG_FIQ=y
 CONFIG_ATAGS=y
 CONFIG_KUSER_HELPERS=y
+CONFIG_ARM_ERRATA_643719=y
 CONFIG_RASPBERRYPI_FIRMWARE=y
 CONFIG_BRCM_CHAR_DRIVERS=y
 CONFIG_BCM2708_VCHIQ=y

target/linux/config/Config.in.dma

@@ -38,8 +38,12 @@ config ADK_KERNEL_BCM_VC_CMA
 config ADK_KERNEL_BCM_VCIO
 	bool
 
+config ADK_KERNEL_DMA_BCM2708_LEGACY
+	bool
+
 config ADK_KERNEL_DMA_BCM2708
         bool
+	select ADK_KERNEL_DMA_BCM2708_LEGACY
         select ADK_KERNEL_DMADEVICES
 	select ADK_KERNEL_CMA
 	select ADK_KERNEL_CMA_SIZE_SEL_MBYTES