cpu: Remove ISA information from CPU map XML

The information is not used anywhere in libvirt.

No functional changes.

src/cpu/cpu_map.xml

@@ -1385,31 +1385,26 @@
 
     <model name='power6'>
       <vendor name='IBM'/>
-      <compat isa='2.05'/>
       <pvr value='0x003e0000'/>
     </model>
 
     <model name='power7'>
       <vendor name='IBM'/>
-      <compat isa='2.06'/>
       <pvr value='0x003f0000'/>
     </model>
 
     <model name='power7+'>
       <vendor name='IBM'/>
-      <compat isa='2.06B'/>
       <pvr value='0x004a0000'/>
     </model>
 
     <model name='power8e'>
       <vendor name='IBM'/>
-      <compat isa='2.07'/>
       <pvr value='0x004b0000'/>
     </model>
 
     <model name='power8'>
       <vendor name='IBM'/>
-      <compat isa='2.07'/>
       <pvr value='0x004d0000'/>
     </model>