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/arm/cpu/arm926ejs/start.S b/arch/arm/cpu/arm926ejs/start.S
index 66a8b65..f5d1582 100644
--- a/arch/arm/cpu/arm926ejs/start.S
+++ b/arch/arm/cpu/arm926ejs/start.S
@@ -142,7 +142,7 @@
 
 .globl _bss_end_ofs
 _bss_end_ofs:
-	.word __bss_end__ - _start
+	.word __bss_end - _start
 
 .globl _end_ofs
 _end_ofs:
@@ -151,7 +151,7 @@
 #ifdef CONFIG_NAND_U_BOOT
 .globl _end
 _end:
-	.word __bss_end__
+	.word __bss_end
 #endif
 
 #ifdef CONFIG_USE_IRQ