riscv: cpu: fu540: Add support for cpu fu540

Add SiFive fu540 cpu to support RISC-V arch

Signed-off-by: Pragnesh Patel <pragnesh.patel@sifive.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Jagan Teki <jagan@amarulasolutions.com>
Tested-by: Jagan Teki <jagan@amarulasolutions.com>
diff --git a/board/sifive/fu540/Kconfig b/board/sifive/fu540/Kconfig
index d41c305..eb5ba31 100644
--- a/board/sifive/fu540/Kconfig
+++ b/board/sifive/fu540/Kconfig
@@ -7,7 +7,7 @@
 	default "sifive"
 
 config SYS_CPU
-	default "generic"
+	default "fu540"
 
 config SYS_CONFIG_NAME
 	default "sifive-fu540"