Add architecture-specific global data

We plan to move architecture-specific data into a separate structure so
that we can make the rest of it common.

As a first step, create struct arch_global_data to hold these fields.
Initially it is empty.

This patch applies to all archs at once. I can split it if this is really
a pain.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sh/include/asm/global_data.h b/arch/sh/include/asm/global_data.h
index 9a2c193..db85d4d 100644
--- a/arch/sh/include/asm/global_data.h
+++ b/arch/sh/include/asm/global_data.h
@@ -27,6 +27,10 @@
 #ifndef	__ASM_SH_GLOBALDATA_H_
 #define __ASM_SH_GLOBALDATA_H_
 
+/* Architecture-specific global data */
+struct arch_global_data {
+};
+
 typedef	struct global_data
 {
 	bd_t		*bd;
@@ -42,6 +46,7 @@
 	unsigned long	env_valid;	/* Checksum of Environment valid */
 	void		**jt;		/* Standalone app jump table */
 	char		env_buf[32];	/* buffer for getenv() before reloc. */
+	struct arch_global_data arch;	/* architecture-specific data */
 } gd_t;
 
 #include <asm-generic/global_data_flags.h>