sh: Get multiple boards in one image working again.

This tidies up the build rules and permits multiple boards to be
linked in to the same kernel. The earlier Kconfig work ensures that
the CPU configuration is consistent across the boards, as this is
the only thing that we can't do dynamically.

Signed-off-by: Paul Mundt <lethal@linux-sh.org>

include/asm-sh/machvec_init.h

@@ -14,6 +14,6 @@
 
 #define __initmv __attribute__((unused,__section__ (".machvec.init")))
 #define ALIAS_MV(system) \
-  asm(".global sh_mv\nsh_mv = mv_"#system );
+  asm(".weak sh_mv\nsh_mv = mv_"#system );
 
 #endif /* __SH_MACHVEC_INIT_H */