Cleanup: fix "MHz" spelling

Signed-off-by: Wolfgang Denk <wd@denx.de>
diff --git a/cpu/ppc4xx/miiphy.c b/cpu/ppc4xx/miiphy.c
index 84b1bbe..01710e7 100644
--- a/cpu/ppc4xx/miiphy.c
+++ b/cpu/ppc4xx/miiphy.c
@@ -301,7 +301,7 @@
 
 	sta_reg = reg;		/* reg address */
 
-	/* set clock (50Mhz) and read flags */
+	/* set clock (50MHz) and read flags */
 #if defined(CONFIG_440GX) || defined(CONFIG_440SPE) || \
     defined(CONFIG_440EPX) || defined(CONFIG_440GRX) || \
     defined(CONFIG_460EX) || defined(CONFIG_460GT) || \