nir: replace magic numbers with M_PI

we define it inside 'include/c99_math.h' so it is safe to use.

Signed-off-by: Karol Herbst <kherbst@redhat.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>

src/compiler/nir/nir_builtin_builder.h

 static inline nir_ssa_def *
 nir_degrees(nir_builder *b, nir_ssa_def *val)
 {
-   return nir_fmul_imm(b, val, 57.2957795131);
+   return nir_fmul_imm(b, val, 180.0 / M_PI);
 }
 
 static inline nir_ssa_def *
 static inline nir_ssa_def *
 nir_radians(nir_builder *b, nir_ssa_def *val)
 {
-   return nir_fmul_imm(b, val, 0.01745329251);
+   return nir_fmul_imm(b, val, M_PI / 180.0);
 }
 
 #endif /* NIR_BUILTIN_BUILDER_H */