ARM: dts: at91: sama5d4 xplained: properly mux phy interrupt

No interrupt were received from the phy because PIOE 1 may not be properly
muxed. It prevented proper link detection, especially since commit
321beec5 ("net: phy: Use interrupts when available in NOLINK state")
disables polling.

Cc: <stable@vger.kernel.org> # 4.4
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>