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/u-boot.lds b/arch/avr32/cpu/u-boot.lds
index 0b16d2a..d096424 100644
--- a/arch/avr32/cpu/u-boot.lds
+++ b/arch/avr32/cpu/u-boot.lds
@@ -68,5 +68,5 @@
 		*(.bss.*)
 	}
 	. = ALIGN(8);
-	__bss_end__ = .;
+	__bss_end = .;
 }