ARM: dts: bcm2835: Fix labels for GPIO 0,1

According to the schematics for all RPis with a 40 pin header,
the GPIOs 0 and 1 are labeled as ID_SD and ID_SC. In order to
clarify that is a I2C bus, append the third letter.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Reviewed-by: Eric Anholt <eric@anholt.net>