riscv: don't define fenv macros for soft float

As is done for all other soft float ports.

arch/riscv32/bits/fenv.h

@@ -1,3 +1,7 @@
+#ifdef __riscv_float_abi_soft
+#define FE_ALL_EXCEPT   0
+#define FE_TONEAREST    0
+#else
 #define FE_INVALID      16
 #define FE_DIVBYZERO    8
 #define FE_OVERFLOW     4
@@ -10,6 +14,7 @@
 #define FE_DOWNWARD     2
 #define FE_UPWARD       3
 #define FE_TOWARDZERO   1
+#endif
 
 typedef unsigned int fexcept_t;
 typedef unsigned int fenv_t;

arch/riscv64/bits/fenv.h

@@ -1,3 +1,7 @@
+#ifdef __riscv_float_abi_soft
+#define FE_ALL_EXCEPT   0
+#define FE_TONEAREST    0
+#else
 #define FE_INVALID      16
 #define FE_DIVBYZERO    8
 #define FE_OVERFLOW     4
@@ -10,6 +14,7 @@
 #define FE_DOWNWARD     2
 #define FE_UPWARD       3
 #define FE_TOWARDZERO   1
+#endif
 
 typedef unsigned int fexcept_t;
 typedef unsigned int fenv_t;