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/74xx_7xx/start.S b/arch/powerpc/cpu/74xx_7xx/start.S
index 985e1ce..f6011fc 100644
--- a/arch/powerpc/cpu/74xx_7xx/start.S
+++ b/arch/powerpc/cpu/74xx_7xx/start.S
@@ -77,7 +77,7 @@
 	GOT_ENTRY(transfer_to_handler)
 
 	GOT_ENTRY(__init_end)
-	GOT_ENTRY(_end)
+	GOT_ENTRY(__bss_end__)
 	GOT_ENTRY(__bss_start)
 	END_GOT
 
@@ -722,7 +722,7 @@
 	 * Now clear BSS segment
 	 */
 	lwz	r3,GOT(__bss_start)
-	lwz	r4,GOT(_end)
+	lwz	r4,GOT(__bss_end__)
 
 	cmplw	0, r3, r4
 	beq	6f
diff --git a/arch/powerpc/cpu/74xx_7xx/u-boot.lds b/arch/powerpc/cpu/74xx_7xx/u-boot.lds
index 8429f33..24823cd 100644
--- a/arch/powerpc/cpu/74xx_7xx/u-boot.lds
+++ b/arch/powerpc/cpu/74xx_7xx/u-boot.lds
@@ -87,6 +87,6 @@
    *(COMMON)
    . = ALIGN(4);
   }
-  _end = . ;
+  __bss_end__ = . ;
   PROVIDE (end = .);
 }