Move uninitialized_var() macro from ubi_uboot.h to compiler.h

This is needed so that we could use this macro for non-UBI code.

Signed-off-by: Anton Vorontsov <avorontsov@ru.mvista.com>
diff --git a/include/compiler.h b/include/compiler.h
index 272fd3c..e602cce 100644
--- a/include/compiler.h
+++ b/include/compiler.h
@@ -122,4 +122,7 @@
 
 #endif
 
+/* compiler options */
+#define uninitialized_var(x)		x = x
+
 #endif