ppc4xx: Fix missing freqOPB for 405EP

In cpu/ppc4xx/speed.c initialization of sysInfo->freqOPB for 405EP was
left out for no obvious reason.

Signed-off-by: Dirk Eibach <eibach@gdsys.de>
Signed-off-by: Stefan Roese <sr@denx.de>

cpu/ppc4xx/speed.c

@@ -867,6 +867,8 @@ void get_sys_info (PPC4xx_SYS_INFO * sysInfo)
 
 	sysInfo->freqEBC = sysInfo->freqPLB / sysInfo->pllExtBusDiv;
 
+	sysInfo->freqOPB = sysInfo->freqPLB / sysInfo->pllOpbDiv;
+
 	sysInfo->freqUART = sysInfo->freqProcessor * pllmr0_ccdv;
 }