arm: move C runtime setup code in crt0.S

Move all the C runtime setup code from every start.S
in arch/arm into arch/arm/lib/crt0.S. This covers
the code sequence from setting up the initial stack
to calling into board_init_r().

Also, rewrite the C runtime setup and make functions
board_init_*() and relocate_code() behave according to
normal C semantics (no jumping across the C stack any
more, etc).

Some SPL targets had to be touched because they use
start.S explicitly or for some reason; the relevant
maintainers and custodians are cc:ed.

Signed-off-by: Albert ARIBAUD <albert.u.boot@aribaud.net>

lib/asm-offsets.c

@@ -28,5 +28,19 @@ int main(void)
 	DEFINE(GENERATED_BD_INFO_SIZE,
 		(sizeof(struct bd_info) + 15) & ~15);
 
+	DEFINE(GD_SIZE, sizeof(struct global_data));
+
+	DEFINE(GD_BD, offsetof(struct global_data, bd));
+
+#if defined(CONFIG_ARM)
+
+	DEFINE(GD_RELOCADDR, offsetof(struct global_data, relocaddr));
+
+	DEFINE(GD_RELOC_OFF, offsetof(struct global_data, reloc_off));
+
+	DEFINE(GD_START_ADDR_SP, offsetof(struct global_data, start_addr_sp));
+
+#endif
+
 	return 0;
 }