AT91: Use AT91_CPU_CLOCK in displays

Introduce AT91_CPU_CLOCK and use it for displaying the CPU
speed in the LCD driver.

Also make AT91_MAIN_CLOCK and AT91_MASTER_CLOCK reflect the
corresponding board clocks.

Signed-off-by: Stelian Pop <stelian@popies.net>
diff --git a/board/atmel/at91sam9rlek/at91sam9rlek.c b/board/atmel/at91sam9rlek/at91sam9rlek.c
index 992dd4c..b6fef9d 100644
--- a/board/atmel/at91sam9rlek/at91sam9rlek.c
+++ b/board/atmel/at91sam9rlek/at91sam9rlek.c
@@ -197,7 +197,7 @@
 	lcd_printf ("at91support@atmel.com\n");
 	lcd_printf ("%s CPU at %s MHz\n",
 		AT91_CPU_NAME,
-		strmhz(temp, AT91_MAIN_CLOCK));
+		strmhz(temp, AT91_CPU_CLOCK));
 
 	dram_size = 0;
 	for (i = 0; i < CONFIG_NR_DRAM_BANKS; i++)