include: Include headers where needed

A number of headers neglect to include everything they need.  They
compile only if the headers they need are already included from
elsewhere.  Fix that.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Alistair Francis <alistair.francis@wdc.com>
Message-Id: <20221222120813.727830-3-armbru@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/include/hw/riscv/sifive_u.h b/include/hw/riscv/sifive_u.h
index e680d61..a67328f 100644
--- a/include/hw/riscv/sifive_u.h
+++ b/include/hw/riscv/sifive_u.h
@@ -19,6 +19,8 @@
 #ifndef HW_SIFIVE_U_H
 #define HW_SIFIVE_U_H
 
+#include "hw/boards.h"
+#include "hw/cpu/cluster.h"
 #include "hw/dma/sifive_pdma.h"
 #include "hw/net/cadence_gem.h"
 #include "hw/riscv/riscv_hart.h"