rockchip: rk3288: Move rk3288_detect_reset_reason to soc file

The rk3288_detect_reset_reason() is per-SoC operation, move
it to rk3288.c, and extend the rk_board_late_init() with
rk3288_board_late_init() to make all the board works fine
as before.

Signed-off-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/board/chipspark/popmetal_rk3288/popmetal-rk3288.c b/board/chipspark/popmetal_rk3288/popmetal-rk3288.c
index 9ba1fbd..47b921a 100644
--- a/board/chipspark/popmetal_rk3288/popmetal-rk3288.c
+++ b/board/chipspark/popmetal_rk3288/popmetal-rk3288.c
@@ -8,7 +8,7 @@
 
 #define GPIO7A3_HUB_RST	227
 
-int rk_board_late_init(void)
+int rk3288_board_late_init(void)
 {
 	int ret;