ARM1136: Introduce CONFIG_PRELOADER macro.

Currently CONFIG_ONENAND_IPL is used in a number of #ifdef's
in start.S. In preparation for adding support for NAND SPL
the macro CONFIG_PRELOADER is introducted and replaces the
CONFIG_ONENAND_IPL in start.S.

Signed-off-by: Magnus Lilja <lilja.magnus@gmail.com>
diff --git a/README b/README
index 561c100..0e84337 100644
--- a/README
+++ b/README
@@ -2702,6 +2702,11 @@
 		some other boot loader or by a debugger which
 		performs these initializations itself.
 
+- CONFIG_PRELOADER
+
+		Modifies the behaviour of start.S when compiling a loader
+		that is executed before the actual U-Boot. E.g. when
+		compiling a NAND SPL.
 
 Building the Software:
 ======================