board: sifive: Rename spl_soc_init() to spl_dram_init()

Rename spl_soc_init() to spl_dram_init() because the generic function
name does not reflect what the function actually does. Also
spl_dram_init() is commonly used for dram initialization and should be
called from board_init_f().

Signed-off-by: Lukas Funke <lukas.funke@weidmueller.com>
Reviewed-by: Leo Yu-Chi Liang <ycliang@andestech.com>
diff --git a/arch/riscv/cpu/fu740/spl.c b/arch/riscv/cpu/fu740/spl.c
index c6816e9..16b307f 100644
--- a/arch/riscv/cpu/fu740/spl.c
+++ b/arch/riscv/cpu/fu740/spl.c
@@ -10,7 +10,7 @@
 
 #define CSR_U74_FEATURE_DISABLE	0x7c1
 
-int spl_soc_init(void)
+int spl_dram_init(void)
 {
 	int ret;
 	struct udevice *dev;