target/riscv: rationalise softfloat includes

We should avoid including the whole of softfloat headers in cpu.h and
explicitly include it only where we will be calling softfloat
functions. We can use the -types.h and -helpers.h in cpu.h for the few
bits that are global.

Backports commit 135b03cb9defbd080b8834b30e3d45bed00c6137 from qemu

qemu/target/riscv/cpu.c

@@ -22,6 +22,7 @@
 #include "cpu.h"
 #include "exec/exec-all.h"
 #include "qapi/error.h"
+#include "fpu/softfloat-helpers.h"
 
 #include "uc_priv.h"
 

qemu/target/riscv/cpu.h

@@ -25,7 +25,7 @@
 #include "qemu-common.h"
 #include "qom/cpu.h"
 #include "exec/cpu-defs.h"
-#include "fpu/softfloat.h"
+#include "fpu/softfloat-types.h"
 
 #define TCG_GUEST_DEFAULT_MO 0
 

qemu/target/riscv/fpu_helper.c

@@ -21,6 +21,7 @@
 #include "qemu/host-utils.h"
 #include "exec/exec-all.h"
 #include "exec/helper-proto.h"
+#include "fpu/softfloat.h"
 
 target_ulong riscv_cpu_get_fflags(CPURISCVState *env)
 {