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/avr32/include/asm/sections.h b/arch/avr32/include/asm/sections.h
index fe819b2..3f15788 100644
--- a/arch/avr32/include/asm/sections.h
+++ b/arch/avr32/include/asm/sections.h
@@ -27,6 +27,6 @@
 extern char _text[], _etext[];
 extern char _data[], __data_lma[], _edata[], __edata_lma[];
 extern char __got_start[], __got_lma[], __got_end[];
-extern char _end[];
+extern char __bss_end__[];
 
 #endif /* __ASM_AVR32_SECTIONS_H */