ram: rockchip: fix typo in KConfig option label

RAM_PX30_DDR4 is for DDR4 support and not DDR3 so let's fix the typo.

Fixes: 2db36c64bd5a ("ram: rockchip: px30: add a config-based ddr selection")
Cc: Quentin Schulz <foss+uboot@0leil.net>
Signed-off-by: Quentin Schulz <quentin.schulz@theobroma-systems.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/drivers/ram/rockchip/Kconfig b/drivers/ram/rockchip/Kconfig
index c459bbf..c29d5e8 100644
--- a/drivers/ram/rockchip/Kconfig
+++ b/drivers/ram/rockchip/Kconfig
@@ -23,7 +23,7 @@
 	  initialization, configurations and etc.
 
 config RAM_PX30_DDR4
-	bool "DDR3 support for Rockchip PX30"
+	bool "DDR4 support for Rockchip PX30"
 	depends on RAM_ROCKCHIP && ROCKCHIP_PX30
 	help
 	  This enables DDR4 sdram support instead of the default DDR3 support