arm: Move lastinc 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/mb86r0x/timer.c b/arch/arm/cpu/arm926ejs/mb86r0x/timer.c
index 1f1900e..c6486c1 100644
--- a/arch/arm/cpu/arm926ejs/mb86r0x/timer.c
+++ b/arch/arm/cpu/arm926ejs/mb86r0x/timer.c
@@ -36,7 +36,7 @@
 DECLARE_GLOBAL_DATA_PTR;
 
 #define timestamp gd->arch.tbl
-#define lastdec gd->lastinc
+#define lastdec gd->arch.lastinc
 
 static inline unsigned long long tick_to_time(unsigned long long tick)
 {