riscv: Enable SPI flash env for SiFive Unmatched.

Enable saving environment to SPI flash memory on SiFive
Unmatched.

Signed-off-by: Thomas Skibo <thomas-git@skibo.net>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>

arch/riscv/cpu/fu740/Kconfig

@@ -40,3 +40,16 @@ config SIFIVE_FU740
 	imply DM_I2C
 	imply SYS_I2C_OCORES
 	imply SPL_I2C
+
+if ENV_IS_IN_SPI_FLASH
+
+config ENV_OFFSET
+	default 0x505000
+
+config ENV_SIZE
+	default 0x20000
+
+config ENV_SECT_SIZE
+	default 0x10000
+
+endif # ENV_IS_IN_SPI_FLASH

board/sifive/unmatched/Kconfig

@@ -26,6 +26,7 @@ config SPL_OPENSBI_LOAD_ADDR
 config BOARD_SPECIFIC_OPTIONS # dummy
 	def_bool y
 	select SIFIVE_FU740
+	select ENV_IS_IN_SPI_FLASH
 	select SUPPORT_SPL
 	select RESET_SIFIVE
 	select BINMAN