Convert CONFIG_SYS_CONSOLE_ENV_OVERWRITE to Kconfig

This converts the following to Kconfig:
   CONFIG_SYS_CONSOLE_ENV_OVERWRITE

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/socfpga_vining_fpga_defconfig b/configs/socfpga_vining_fpga_defconfig
index 79b0cba..c9b0178 100644
--- a/configs/socfpga_vining_fpga_defconfig
+++ b/configs/socfpga_vining_fpga_defconfig
@@ -7,6 +7,7 @@
 CONFIG_FIT=y
 CONFIG_BOOTDELAY=5
 CONFIG_SYS_CONSOLE_IS_IN_ENV=y
+CONFIG_SYS_CONSOLE_ENV_OVERWRITE=y
 CONFIG_VERSION_VARIABLE=y
 # CONFIG_DISPLAY_BOARDINFO is not set
 CONFIG_SPL=y