8xxx-fdt: set ns16550 clock from CFG_NS16550_CLK, not bi_busfreq

Some boards that have external 16550 UARTs don't have a direct
tie between bi_busfreq and the clock used for the UARTs.  Boards
that do have such a tie should set CFG_NS16550_CLK to be
get_bus_freq(0) -- which most of them do already.

Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
Acked-by: Kim Phillips <kim.phillips@freescale.com>
diff --git a/cpu/mpc85xx/fdt.c b/cpu/mpc85xx/fdt.c
index c8d2c6a..c159934 100644
--- a/cpu/mpc85xx/fdt.c
+++ b/cpu/mpc85xx/fdt.c
@@ -229,7 +229,7 @@
 
 #ifdef CFG_NS16550
 	do_fixup_by_compat_u32(blob, "ns16550",
-		"clock-frequency", bd->bi_busfreq, 1);
+		"clock-frequency", CFG_NS16550_CLK, 1);
 #endif
 
 #ifdef CONFIG_CPM2