ARM: dts: silk: Add r1ex24002 EEPROM to DT

Extend the Silk board support to include U14 which is an I2C based EEPROM
hooked up to the I2C1 bus.

Signed-off-by: Magnus Damm <damm+renesas@opensource.se>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>