powerpc/8xxx: Replace fsl_ddr_get_mem_data_rate with get_ddr_freq()

Every 85xx board implements fsl_ddr_get_mem_data_rate via get_ddr_freq()
and every 86xx board uses get_bus_freq().  If implement get_ddr_freq()
as a static inline to call get_bus_freq() we can remove
fsl_ddr_get_mem_data_rate altogether and just call get_ddr_freq()
directly.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/board/xes/xpedite517x/ddr.c b/board/xes/xpedite517x/ddr.c
index 1d57d09..981bf41 100644
--- a/board/xes/xpedite517x/ddr.c
+++ b/board/xes/xpedite517x/ddr.c
@@ -32,11 +32,6 @@
 		sizeof(ddr2_spd_eeprom_t));
 }
 
-unsigned int fsl_ddr_get_mem_data_rate(void)
-{
-	return get_bus_freq(0);
-}
-
 void fsl_ddr_get_spd(ddr2_spd_eeprom_t *ctrl_dimms_spd,
 			unsigned int ctrl_num)
 {
@@ -144,7 +139,7 @@
 	unsigned int datarate;
 
 	get_sys_info(&sysinfo);
-	datarate = fsl_ddr_get_mem_data_rate() / 1000000;
+	datarate = get_ddr_freq(0) / 1000000;
 
 	for (i = 0; i < ARRAY_SIZE(bopts_ctrl[ctrl_num]); i++) {
 		if ((bopts[i].datarate_mhz_low <= datarate) &&