ARM: dts: at91: sama5: Add the sfr node

For sama5d2, add the sfr node with syscon support.

In order to access the SFR_UTMICKTRIM register for the utmi clock
driver, add the phandle property for the utmi node to point to the
sfr node.

Signed-off-by: Wenyou Yang <wenyou.yang@microchip.com>