ARM: dts: at91: add dma1 definition to sama5d2

The sama5d2 SoC has a second DMA controller and can be used just like DMA0.
By default both DMA controllers are configured as "Secure" in
MATRIX_SPSELR so we can use whichever we want in a "single Secure World"
configuration.
Surprisingly the DMA1 has a lower address than DMA0. To avoid confusion
place it after DMA0 node anyway.

Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>