vmlinux.lds.h: Allow architectures to add sections to the front of .bss

Follow-on MIPS patch will put an object here that needs 64K alignment
to minimize padding.

For those architectures that don't define BSS_FIRST_SECTIONS, there is
no change.
Signed-off-by: David Daney <david.daney@cavium.com>
Cc: linux-mips@linux-mips.org
Cc: linux-arch@vger.kernel.org,
Cc: linux-kernel@vger.kernel.org
Acked-by: Arnd Bergmann <arnd@arndb.de>
Patchwork: https://patchwork.linux-mips.org/patch/4221/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

include/asm-generic/vmlinux.lds.h

@@ -530,9 +530,18 @@
 		*(.scommon)						\
 	}
 
+/*
+ * Allow archectures to redefine BSS_FIRST_SECTIONS to add extra
+ * sections to the front of bss.
+ */
+#ifndef BSS_FIRST_SECTIONS
+#define BSS_FIRST_SECTIONS
+#endif
+
 #define BSS(bss_align)							\
 	. = ALIGN(bss_align);						\
 	.bss : AT(ADDR(.bss) - LOAD_OFFSET) {				\
+		BSS_FIRST_SECTIONS					\
 		*(.bss..page_aligned)					\
 		*(.dynbss)						\
 		*(.bss)							\