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/arch/arm/cpu/u-boot.lds b/arch/arm/cpu/u-boot.lds
index 4da5d24..87c2de2 100644
--- a/arch/arm/cpu/u-boot.lds
+++ b/arch/arm/cpu/u-boot.lds
@@ -60,7 +60,12 @@
 		*(.__rel_dyn_end)
 	}
 
-	_end = .;
+	.end :
+	{
+		*(.__end)
+	}
+
+	_image_binary_end = .;
 
 	/*
 	 * Deprecated: this MMU section is used by pxa at present but
@@ -91,7 +96,7 @@
 		KEEP(*(.__bss_end));
 	}
 
-	.dynsym _end : { *(.dynsym) }
+	.dynsym _image_binary_end : { *(.dynsym) }
 	.dynbss : { *(.dynbss) }
 	.dynstr : { *(.dynstr*) }
 	.dynamic : { *(.dynamic*) }