arm: make _end compiler-generated

This prevents references to _end from generating absolute
relocation records.

This change is binary invariant for ARM targets.

Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
diff --git a/board/davinci/da8xxevm/u-boot-spl-da850evm.lds b/board/davinci/da8xxevm/u-boot-spl-da850evm.lds
index 5480d1f..de21a13 100644
--- a/board/davinci/da8xxevm/u-boot-spl-da850evm.lds
+++ b/board/davinci/da8xxevm/u-boot-spl-da850evm.lds
@@ -49,5 +49,9 @@
 	} >.sram
 
 	__image_copy_end = .;
-	_end = .;
+
+	.end :
+	{
+		*(.__end)
+	}
 }