Replace __bss_end__ with __bss_end

Note this is a tree-wide change affecting multiple architectures.

At present we use __bss_start, but mostly __bss_end__. This seems
inconsistent and in a number of places __bss_end is used instead.

Change to use __bss_end for the BSS end symbol throughout U-Boot. This
makes it possible to use the asm-generic/sections.h file on all
archs.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/avr32/cpu/start.S b/arch/avr32/cpu/start.S
index 71cbc52..c8decea 100644
--- a/arch/avr32/cpu/start.S
+++ b/arch/avr32/cpu/start.S
@@ -244,7 +244,7 @@
 	/* zero out .bss */
 	mov	r0, 0
 	mov	r1, 0
-	lda.w	r9, __bss_end__
+	lda.w	r9, __bss_end
 	sub	r9, r8
 1:	st.d	r10++, r0
 	sub	r9, 8