powerpc/83xx: Fix MCU support merge issue in mpc8349emitx.dts

Just found the merge issue in 44274698


("powerpc/83xx: Add support for MCU microcontroller in .dts files"):
the commit adds the MCU controller node into the DMA node, which is
wrong because the MCU sits on the I2C bus. Fix this by moving the MCU
node into the I2C controller node.

The original patch[1] was OK though. ;-)

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>