ARM: dts: at91: vinco: fix I2C warning bus unit address

w+arch/arm/dts/.at91-vinco.dtb.pre.tmp:131.18-134.7: Warning (i2c_bus_reg): /ahb/apb/i2c@f8024000/rtc@64: I2C bus unit address format error, expected "32"

Signed-off-by: Eugen Hristev <eugen.hristev@microchip.com>