ram: rockchip: Fix Kconfig dependency for RAM_ROCKCHIP_DEBUG

There is no reason to show RAM_ROCKCHIP_DEBUG entry in other .config files
as I see it for Xilinx ZynqMP.

\# CONFIG_U_QE is not set
\# CONFIG_RAM is not set
CONFIG_RAM_ROCKCHIP_DEBUG=y

Add missing dependency on RAM_ROCKCHIP driver.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
diff --git a/drivers/ram/rockchip/Kconfig b/drivers/ram/rockchip/Kconfig
index b75d581..8e97c2f 100644
--- a/drivers/ram/rockchip/Kconfig
+++ b/drivers/ram/rockchip/Kconfig
@@ -13,6 +13,7 @@
 
 config RAM_ROCKCHIP_DEBUG
 	bool "Rockchip ram drivers debugging"
+	depends on RAM_ROCKCHIP
 	default y
 	help
 	  This enables debugging ram driver API's for the platforms