arm: generalize lib/bss.c into lib/sections.c

File arch/arm/lib/bss.c was initially defined for BSS only,
but is now going to also contain definitions for other
section-boundary-related symbols, so rename it for better
accuracy.

Also, remove useless 'used' attributes.

Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
Tested-by: Lubomir Popov <lpopov@mm-sol.com>
Tested-by: Jeroen Hofstee <jeroen@myspectrum.nl>
Reviewed-by: Benoît Thébaudeau <benoit.thebaudeau@advansee.com>

arch/arm/lib/Makefile

@@ -43,7 +43,7 @@ SOBJS-y += relocate.o
 ifndef CONFIG_SYS_GENERIC_BOARD
 COBJS-y	+= board.o
 endif
-COBJS-y += bss.o
+COBJS-y += sections.o
 
 COBJS-y	+= bootm.o
 COBJS-$(CONFIG_OF_LIBFDT) += bootm-fdt.o

arch/arm/lib/sections.c

@@ -35,5 +35,5 @@
  * aliasing warnings.
  */
 
-char __bss_start[0] __attribute__((used, section(".__bss_start")));
-char __bss_end[0] __attribute__((used, section(".__bss_end")));
+char __bss_start[0] __attribute__((section(".__bss_start")));
+char __bss_end[0] __attribute__((section(".__bss_end")));