mx6: Fix definition of IOMUXC_GPR12_DEVICE_TYPE_RC

mx6: Fix definition of IOMUXC_GPR12_DEVICE_TYPE_RC

mx6 reference manual incorrectly states that the DEVICE_TYPE field of
IOMUXC_GPR12 register should be configured as '0010' for setting the PCI
controller in RC mode. The correct value should be '0100' instead.

This also aligns with the same value used in the mx6 pci kernel driver.

Signed-off-by: Fabio Estevam <fabio.estevam@freescale.com>
Acked-by: Marek Vasut <marex@denx.de>
Acked-by: Stefano Babic <sbabic@denx.de>