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/drivers/clk/sifive/fu740-prci.h b/drivers/clk/sifive/fu740-prci.h
new file mode 100644
index 0000000..b74f078
--- /dev/null
+++ b/drivers/clk/sifive/fu740-prci.h
@@ -0,0 +1,22 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * Copyright (C) 2020-2021 SiFive, Inc.
+ * Zong Li
+ * Pragnesh Patel
+ */
+
+#ifndef __SIFIVE_CLK_FU740_PRCI_H
+#define __SIFIVE_CLK_FU740_PRCI_H
+
+#include "sifive-prci.h"
+
+#define NUM_CLOCK_FU740		9
+
+extern struct __prci_clock __prci_init_clocks_fu740[NUM_CLOCK_FU740];
+
+static const struct prci_clk_desc prci_clk_fu740 = {
+	.clks = __prci_init_clocks_fu740,
+	.num_clks = ARRAY_SIZE(__prci_init_clocks_fu740),
+};
+
+#endif /* __SIFIVE_CLK_FU740_PRCI_H */