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>

arch/avr32/include/asm/sections.h

@@ -27,6 +27,6 @@
 extern char _text[], _etext[];
 extern char _data[], __data_lma[], _edata[], __edata_lma[];
 extern char __got_start[], __got_lma[], __got_end[];
-extern char __bss_end__[];
+extern char __bss_end[];
 
 #endif /* __ASM_AVR32_SECTIONS_H */