rename _end to __bss_end__

Currently, _end is used for end of BSS section.  We want _end to mean
end of u-boot image, so we rename _end to __bss_end__ first.

Signed-off-by: Po-Yu Chuang <ratbert@faraday-tech.com>
diff --git a/arch/powerpc/cpu/mpc5xx/u-boot.lds b/arch/powerpc/cpu/mpc5xx/u-boot.lds
index 69bd7aa..e02b213 100644
--- a/arch/powerpc/cpu/mpc5xx/u-boot.lds
+++ b/arch/powerpc/cpu/mpc5xx/u-boot.lds
@@ -91,7 +91,7 @@
    . = ALIGN(4);
   }
 
-  _end = . ;
+  __bss_end__ = . ;
   PROVIDE (end = .);
   . = env_start;
   .ppcenv :