rockchip: px30: Add EVB_PX30 Kconfig help

TARGET_EVB_PX30 can be possible to use other px30 boards.

Add the help text for existing EVB, so-that the new boards
which are resuing this config option can mention their board
help text.

This would help to track which boards are using EVB_PX30 config.

Signed-off-by: Jagan Teki <jagan@amarulasolutions.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
diff --git a/arch/arm/mach-rockchip/px30/Kconfig b/arch/arm/mach-rockchip/px30/Kconfig
index f5373c6..6cd65df 100644
--- a/arch/arm/mach-rockchip/px30/Kconfig
+++ b/arch/arm/mach-rockchip/px30/Kconfig
@@ -2,6 +2,11 @@
 
 config TARGET_EVB_PX30
 	bool "EVB_PX30"
+	help
+	  This target config option used for below listed px30 boards.
+
+	  EVB_PX30:
+	  * EVB_PX30 is an evaluation board for Rockchip PX30.
 
 config TARGET_ODROID_GO2
 	bool "ODROID_GO2"