powerpc: mpc83xx: fdt: Use get_serial_clock()

Replace the hard-coded CONFIG_SYS_NS16550_CLK value for the FDT fixup
with the previously introduced get_serial_clock function

This will make it possible to activate DM for serial devices on MPC83xx
later on.

Signed-off-by: Mario Six <mario.six@gdsys.cc>
1 file changed