configs: stm32: Enable CONFIG_ENV_VARS_UBOOT_CONFIG

Enable CONFIG_ENV_VARS_UBOOT_CONFIG for all STM32 boards
It allows to retrieve the SoC name into the "soc" environment
variable.

Signed-off-by: Christophe Priouzeau <christophe.priouzeau@st.com>
Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Reviewed-by: Vikas Manocha <vikas.manocha@st.com>
diff --git a/include/configs/stm32h743-eval.h b/include/configs/stm32h743-eval.h
index 531de70..1494203 100644
--- a/include/configs/stm32h743-eval.h
+++ b/include/configs/stm32h743-eval.h
@@ -39,6 +39,8 @@
 #define CONFIG_BOOTARGS							\
 	"console=ttyS0,115200 earlyprintk consoleblank=0 ignore_loglevel"
 
+#define CONFIG_ENV_VARS_UBOOT_CONFIG
+
 /*
  * Command line configuration.
  */