linux-user: set default PPC64 CPU

The default CPU for pseries has been set to POWER9 by default.
We can use the same default for linux-user

Signed-off-by: Laurent Vivier <laurent@vivier.eu>
Message-Id: <20190609143521.19374-2-laurent@vivier.eu>
Signed-off-by: Laurent Vivier <laurent@vivier.eu>

linux-user/ppc/target_elf.h

@@ -10,7 +10,7 @@
 static inline const char *cpu_get_model(uint32_t eflags)
 {
 #ifdef TARGET_PPC64
-    return "POWER8";
+    return "POWER9";
 #else
     return "750";
 #endif