[bsp][stm32] delete Kconfig $
mainmenu "RT-Thread Configuration"
-config $BSP_DIR
+config BSP_DIR
string
option env="BSP_ROOT"
default "."
-config $RTT_DIR
+config RTT_DIR
string
option env="RTT_ROOT"
default "../../.."
-config $PKGS_DIR
+config PKGS_DIR
string
option env="PKGS_ROOT"
default "packages"
