[SYCL] Add missing special values to exp(complex)

exp(x,NaN) (for any finite x) = (NaN,NaN)
exp(NaN,y) (for any nonzero y) = (NaN,NaN)
exp(x,+∞) (for any finite x) = (NaN,NaN)

https://en.cppreference.com/w/cpp/numeric/complex/exp
E2E: intel#15666

libdevice/fallback-complex-fp64.cpp

@@ -149,8 +149,14 @@ double __complex__ __devicelib_cexp(double __complex__ z) {
         z_imag = NAN;
       return CMPLX(z_real, z_imag);
     }
-  } else if (__spirv_IsNan(z_real) && (z_imag == 0.0)) {
-    return z;
+  } else if (__spirv_IsNan(z_real)) {
+    if (z_imag == 0.0)
+      return z;
+    else /*z_imag != 0.0 */
+      return CMPLX(NAN, NAN);
+  } else if (__spirv_IsFinite(z_real)) {
+    if (__spirv_IsNan(z_imag) || __spirv_IsInf(z_imag))
+      return CMPLX(NAN, NAN);
   }
   double __e = __spirv_ocl_exp(z_real);
   double ret_real = __e * __spirv_ocl_cos(z_imag);