Revert "SWDEV-554608 - Add hipHostRegisterIoMemory for hipHostRegister (#1266…" (#1397)

This reverts commit 7f746fc.

Author: JeniferC99

include/hip/hip_runtime_api.h

@@ -899,10 +899,7 @@ enum hipLimit_t {
  * can be obtained with #hipHostGetDevicePointer.*/
 #define hipHostRegisterMapped 0x2
 
-/** The passed memory pointer is treated as pointing to some memory-mapped I/O space, e.g.
- * belonging to a third-party PCIe device, and it will be marked as non cache-coherent and 
- * contiguous.
- * */
+/** Not supported.*/
 #define hipHostRegisterIoMemory 0x4
 
 /** This flag is ignored On AMD devices.*/