global: Migrate CONFIG_PL011_CLOCK to CFG

Perform a simple rename of CONFIG_PL011_CLOCK to CFG_PL011_CLOCK

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/README b/README
index 0561835..8354cf5 100644
--- a/README
+++ b/README
@@ -413,7 +413,7 @@
 					controller register space
 
 - Serial Ports:
-		CONFIG_PL011_CLOCK
+		CFG_PL011_CLOCK
 
 		If you have Amba PrimeCell PL011 UARTs, set this variable to
 		the clock speed of the UARTs.