[Offload][NFC] Rename src/ -> libomptarget/ (llvm#126573)

Summary:
The name `src` is confusing when combined with the plugins and the newly
added `liboffload`.

Author: jhuber6

offload/CMakeLists.txt

@@ -377,7 +377,7 @@ add_subdirectory(DeviceRTL)
 add_subdirectory(tools)
 
 # Build target agnostic offloading library.
-add_subdirectory(src)
+add_subdirectory(libomptarget)
 
 add_subdirectory(tools/offload-tblgen)
 add_subdirectory(liboffload)

offload/src/CMakeLists.txt renamed to offload/libomptarget/CMakeLists.txt

@@ -655,8 +655,8 @@ EXTERN void *omp_get_mapped_ptr(const void *Ptr, int DeviceNum) {
 
   int NumDevices = omp_get_initial_device();
   if (DeviceNum == NumDevices) {
-    DP("Device %d is initial device, returning Ptr " DPxMOD ".\n",
-           DeviceNum, DPxPTR(Ptr));
+    DP("Device %d is initial device, returning Ptr " DPxMOD ".\n", DeviceNum,
+       DPxPTR(Ptr));
     return const_cast<void *>(Ptr);
   }