fm: fdt: Move fman ucode fixup to driver code

Not only powerpc/mpc85xx but also Freescale Layerscape platforms will
use fdt_fixup_fman_firmware() to insert Fman ucode blob into the device
tree. So move the function to Fman driver code.

Signed-off-by: Gong Qianyu <Qianyu.Gong@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>