adding gfx908 namespace

Change-Id: Ifd45385777be5066c8bfef23ee24bbabadf4dffa

test/tool/metrics.xml

@@ -55,6 +55,8 @@
   <metric name="WRITE_SIZE" expr=((TCC_EA_WRREQ_sum-TCC_EA_WRREQ_64B_sum)*32+TCC_EA_WRREQ_64B_sum*64+WDATA1_SIZE)/1024 descr="The total kilobytes written to the video memory. This is measured with all extra fetches and any cache or memory effects taken into account."></metric>
 </gfx906>
 
+<gfx908 base="gfx9"></gfx908>
+
 <global>
   # GPUBusy         The percentage of time GPU was busy.
   <metric