arm: Move tbl to arch_global_data

Move this field into arch_global_data and tidy up.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/arm/cpu/arm926ejs/spear/timer.c b/arch/arm/cpu/arm926ejs/spear/timer.c
index 1dc7860..06ea65b 100644
--- a/arch/arm/cpu/arm926ejs/spear/timer.c
+++ b/arch/arm/cpu/arm926ejs/spear/timer.c
@@ -38,7 +38,7 @@
 
 DECLARE_GLOBAL_DATA_PTR;
 
-#define timestamp gd->tbl
+#define timestamp gd->arch.tbl
 #define lastdec gd->lastinc
 
 int timer_init(void)