ppc4xx: Rename CONFIG_XILINX_ML300 to CONFIG_XILINX_405

This change helps with better handling with others
Xilinx based platform.

Signed-off-by: Michal Simek <monstr@monstr.eu>
Acked-by: Stefan Roese <sr@denx.de>
diff --git a/cpu/ppc4xx/speed.c b/cpu/ppc4xx/speed.c
index ef47ffc..34bd721 100644
--- a/cpu/ppc4xx/speed.c
+++ b/cpu/ppc4xx/speed.c
@@ -754,7 +754,7 @@
 	return sys_info.freqOPB;
 }
 
-#elif defined(CONFIG_XILINX_ML300)
+#elif defined(CONFIG_XILINX_405)
 extern void get_sys_info (sys_info_t * sysInfo);
 extern ulong get_PCI_freq (void);