ARM change name of defines for AT91 arm926ejs

Configuration defines should be preceeded with CONFIG_SYS_. Renamed
some at91 specific defines to conform to this naming convention:

AT91_CPU_NAME to CONFIG_SYS_AT91_CPU_NAME
AT91_MAIN_CLOCK to CONFIG_SYS_AT91_MAIN_CLOCK

Signed-off-by: Achim Ehrlich <aehrlich@taskit.de>
diff --git a/include/configs/at91sam9260ek.h b/include/configs/at91sam9260ek.h
index ff1e5b3..b89242b 100644
--- a/include/configs/at91sam9260ek.h
+++ b/include/configs/at91sam9260ek.h
@@ -30,7 +30,7 @@
 #define CONFIG_AT91_LEGACY
 
 /* ARM asynchronous clock */
-#define AT91_MAIN_CLOCK		18432000	/* 18.432 MHz crystal */
+#define CONFIG_SYS_AT91_MAIN_CLOCK	18432000	/* 18.432 MHz crystal */
 #define CONFIG_SYS_HZ		1000
 
 #define CONFIG_ARM926EJS	1	/* This is an ARM926EJS Core	*/