ARM: dts: bcm2837-rpi-cm3-io3: Fix GPIO line names for SMPS I2C

The GPIOs 46 & 47 are already used for a I2C interface to a SMPS.
So fix the GPIO line names accordingly.

Fixes: a54fe8a6 ("ARM: dts: add Raspberry Pi Compute Module 3 and IO board")
Signed-off-by: Phil Elwell <phil@raspberrypi.com>
Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>