riscv: sifive: fu740: Support i2c in spl

Enable SPL_I2C_SUPPORT for fu740, and add 'u-boot,dm-spl' property in
i2c node.
Signed-off-by: NZong Li <zong.li@sifive.com>
Reviewed-by: NLeo Yu-Chi Liang <ycliang@andestech.com>

arch/riscv/cpu/fu740/Kconfig

@@ -37,3 +37,4 @@ config SIFIVE_FU740
 	imply PWM_SIFIVE
 	imply DM_I2C
 	imply SYS_I2C_OCORES
+	imply SPL_I2C_SUPPORT

arch/riscv/dts/fu740-c000-u-boot.dtsi

@@ -95,6 +95,10 @@
 	u-boot,dm-spl;
 };
 
+&i2c0 {
+	u-boot,dm-spl;
+};
+
 &eth0 {
 	assigned-clocks = <&prci PRCI_CLK_GEMGXLPLL>;
 	assigned-clock-rates = <125125000>;