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/nios2/cpu/start.S b/arch/nios2/cpu/start.S
index 9b0f52d..bf5d672 100644
--- a/arch/nios2/cpu/start.S
+++ b/arch/nios2/cpu/start.S
@@ -100,12 +100,12 @@
 3:
 
 	/* ZERO BSS/SBSS -- bss and sbss are assumed to be adjacent
-	 * and between __bss_start and _end.
+	 * and between __bss_start and __bss_end__.
 	 */
 	 movhi	r5, %hi(__bss_start)
 	 ori	r5, r5, %lo(__bss_start)
-	 movhi	r6, %hi(_end)
-	 ori	r6, r6, %lo(_end)
+	 movhi	r6, %hi(__bss_end__)
+	 ori	r6, r6, %lo(__bss_end__)
 	 beq	r5, r6, 5f
 
 4:	stwio	r0, 0(r5)
diff --git a/arch/nios2/cpu/u-boot.lds b/arch/nios2/cpu/u-boot.lds
index fe4a2eb..4856bd3 100644
--- a/arch/nios2/cpu/u-boot.lds
+++ b/arch/nios2/cpu/u-boot.lds
@@ -103,7 +103,7 @@
 	  *(.scommon)
 	}
 	. = ALIGN(4);
-	_end = .;
+	__bss_end__ = .;
 	PROVIDE (end = .);
 
 	/* DEBUG -- symbol table, string table, etc. etc.