riscv: lib: implement enable_caches for sifive cache

The enable_caches is a generic hook for architecture-implemented, we
define this function to enable composable cache of sifive platforms.

In sifive_cache, it invokes the generic cache_enable interface of cache
uclass to execute the relative implementation in SiFive ccache driver.

Signed-off-by: Zong Li <zong.li@sifive.com>
Reviewed-by: Rick Chen <rick@andestech.com>
diff --git a/arch/riscv/lib/Makefile b/arch/riscv/lib/Makefile
index c4cc414..06020fc 100644
--- a/arch/riscv/lib/Makefile
+++ b/arch/riscv/lib/Makefile
@@ -10,6 +10,7 @@
 obj-$(CONFIG_CMD_BOOTI) += bootm.o image.o
 obj-$(CONFIG_CMD_GO) += boot.o
 obj-y	+= cache.o
+obj-$(CONFIG_SIFIVE_CACHE) += sifive_cache.o
 ifeq ($(CONFIG_$(SPL_)RISCV_MMODE),y)
 obj-$(CONFIG_$(SPL_)SIFIVE_CLINT) += sifive_clint.o
 obj-$(CONFIG_ANDES_PLIC) += andes_plic.o