rockchip: back-to-bootrom: allow passing a cmd to the bootrom

The BROM supports forcing it to enter download-mode, if an appropriate
result/cmd-word is returned to it.  There already is a series to
support this in review, so this prepares the (newly C-version) of the
back-to-bootrom code to accept a cmd to passed on to the BROM.

All the existing call-sites are adjusted to match the changed function
signature.

Signed-off-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>
Tested-by: Andy Yan <andy.yan@rock-chips.com>
diff --git a/arch/arm/mach-rockchip/rk3188-board-spl.c b/arch/arm/mach-rockchip/rk3188-board-spl.c
index 05d4ae6..8e3b8ae 100644
--- a/arch/arm/mach-rockchip/rk3188-board-spl.c
+++ b/arch/arm/mach-rockchip/rk3188-board-spl.c
@@ -158,7 +158,7 @@
 
 	setup_arm_clock();
 #if CONFIG_IS_ENABLED(ROCKCHIP_BACK_TO_BROM) && !defined(CONFIG_SPL_BOARD_INIT)
-	back_to_bootrom();
+	back_to_bootrom(BROM_BOOT_NEXTSTAGE);
 #endif
 }
 
@@ -219,7 +219,7 @@
 
 	preloader_console_init();
 #if CONFIG_IS_ENABLED(ROCKCHIP_BACK_TO_BROM)
-	back_to_bootrom();
+	back_to_bootrom(BROM_BOOT_NEXTSTAGE);
 #endif
 	return;