[OpenMP] Fixes check for host device number

The implemetation is allowed to return -1 for the host device number.
To be complient with the spec both the device number needs to be checked against both -1
as well as the value returned by omp_get_initial_device.

Author: nicebert

offload/libomptarget/OpenMP/API.cpp

@@ -197,7 +197,7 @@ EXTERN int omp_target_is_present(const void *Ptr, int DeviceNum) {
 }
 
 /// Check whether a pointer is accessible from a device.
-/// Returns true when accessibility is guaranteed otherwise returns false.
+/// Returns true when accessibility is guaranteed otherwise returns false. 
 EXTERN int omp_target_is_accessible(const void *Ptr, size_t Size,
                                     int DeviceNum) {
   TIMESCOPE();
@@ -211,7 +211,7 @@ EXTERN int omp_target_is_accessible(const void *Ptr, size_t Size,
     return false;
   }
 
-  if (DeviceNum == omp_get_initial_device()) {
+  if (DeviceNum == omp_get_initial_device() || DeviceNum == -1) {
     DP("Call to omp_target_is_accessible on host, returning true\n");
     return true;
   }