Improve automated platform detection.

If AMD GPU is installed and detected by driver, default
HIP_PLATFORM to hcc.

bin/hipconfig

@@ -45,10 +45,15 @@ $HSA_PATH='/opt/hsa' unless defined $HSA_PATH;
 #---
 #HIP_PLATFORM controls whether to use NVCC or HCC for compilation:
 $HIP_PLATFORM=$ENV{'HIP_PLATFORM'};
-if (not defined $HIP_PLATFORM and (-e "$CUDA_PATH/bin/nvcc")) {
-    $HIP_PLATFORM="nvcc";
+if (not defined $HIP_PLATFORM) {
+    $NAMDGPUNODES=`cat /sys/class/kfd/kfd/topology/nodes/*/properties 2>/dev/null | grep -c 'simd_count [1-9]'`;
+    
+    if ($NAMDGPUNODES > 0) {
+        $HIP_PLATFORM = "hcc"
+    } else {
+        $HIP_PLATFORM = "nvcc";
+    }
 }
-$HIP_PLATFORM="hcc" unless defined $HIP_PLATFORM;
 
 $HIP_PATH=$ENV{'HIP_PATH'};
 $HIP_PATH=Cwd::realpath (dirname (dirname $0)) unless defined $HIP_PATH;        # use parent directory of this tool