arm: make __bss_start and __bss_end__ compiler-generated

Turn __bss_start and __bss_end__ from linker-generated
to compiler-generated symbols, causing relocations for
these symbols to change type, from R_ARM_ABS32 to
R_ARM_RELATIVE.

This should have no functional impact, as it affects
references to __bss_start and __bss_end__ only before
relocation, and no such references are done.

Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>
diff --git a/arch/arm/lib/Makefile b/arch/arm/lib/Makefile
index 57111af..11c2674 100644
--- a/arch/arm/lib/Makefile
+++ b/arch/arm/lib/Makefile
@@ -39,6 +39,7 @@
 SOBJS-y += crt0.o
 
 ifndef CONFIG_SPL_BUILD
+COBJS-y += bss.o
 COBJS-y	+= board.o
 COBJS-y	+= bootm.o
 COBJS-$(CONFIG_SYS_L2_PL310) += cache-pl310.o