Add agent query for nearest CPU agent

Add agent info query to return nearest CPU agent. This can be used to
determine which CPU agent is in the same NUMA region as the GPU agent.

Change-Id: I5400b4347ffbf4d2a836df31c4de443a38b0ecd1

runtime/hsa-runtime/inc/hsa_ext_amd.h

@@ -399,7 +399,12 @@ typedef enum hsa_amd_agent_info_s {
    * Queries for driver unique identifier.
    * The type of this attribute is uint32_t.
    */
-  HSA_AMD_AGENT_INFO_DRIVER_UID = 0xA112
+  HSA_AMD_AGENT_INFO_DRIVER_UID = 0xA112,
+  /**
+   * Returns the hsa_agent_t of the nearest CPU agent
+   * The type of this attribute is hsa_agent_t.
+   */
+  HSA_AMD_AGENT_INFO_NEAREST_CPU = 0xA113
 } hsa_amd_agent_info_t;
 
 /**