riscv: sifive: unmatched: migrate to text environment

Migrate to the new environment format and drop most of the config.h.

Signed-off-by: Yong-Xuan Wang <yongxuan.wang@sifive.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/sifive_unmatched_defconfig b/configs/sifive_unmatched_defconfig
index 6a95ab3..43fc87d 100644
--- a/configs/sifive_unmatched_defconfig
+++ b/configs/sifive_unmatched_defconfig
@@ -23,7 +23,7 @@
 CONFIG_RISCV_SMODE=y
 CONFIG_FIT=y
 CONFIG_SPL_LOAD_FIT_ADDRESS=0x84000000
-CONFIG_DISTRO_DEFAULTS=y
+CONFIG_BOOTSTD_DEFAULTS=y
 CONFIG_USE_PREBOOT=y
 CONFIG_PREBOOT="setenv fdt_addr ${fdtcontroladdr};fdt addr ${fdtcontroladdr};"
 CONFIG_DEFAULT_FDT_FILE="sifive/hifive-unmatched-a00.dtb"