drivers: clk: add fu740 support

Add fu740 support. One abstract layer is added for supporting
multiple chips such as fu540 and fu740.

Signed-off-by: Green Wan <green.wan@sifive.com>
diff --git a/arch/riscv/cpu/fu540/Kconfig b/arch/riscv/cpu/fu540/Kconfig
index dcf0994..05463b2 100644
--- a/arch/riscv/cpu/fu540/Kconfig
+++ b/arch/riscv/cpu/fu540/Kconfig
@@ -18,7 +18,7 @@
 	imply SPL_LOAD_FIT
 	imply SMP
 	imply CLK_SIFIVE
-	imply CLK_SIFIVE_FU540_PRCI
+	imply CLK_SIFIVE_PRCI
 	imply SIFIVE_SERIAL
 	imply MACB
 	imply MII