target-ppc: Use #define for max slb entries

Instead of opencoding 64 use MAX_SLB_ENTRIES. We don't update the kernel
header here.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Alexander Graf <agraf@suse.de>
diff --git a/target-ppc/cpu.h b/target-ppc/cpu.h
index 422a6bb..26acdba 100644
--- a/target-ppc/cpu.h
+++ b/target-ppc/cpu.h
@@ -405,6 +405,7 @@
     uint64_t vsid;
 };
 
+#define MAX_SLB_ENTRIES         64
 #define SEGMENT_SHIFT_256M      28
 #define SEGMENT_MASK_256M       (~((1ULL << SEGMENT_SHIFT_256M) - 1))
 
@@ -949,7 +950,7 @@
 #if !defined(CONFIG_USER_ONLY)
 #if defined(TARGET_PPC64)
     /* PowerPC 64 SLB area */
-    ppc_slb_t slb[64];
+    ppc_slb_t slb[MAX_SLB_ENTRIES];
     int32_t slb_nr;
 #endif
     /* segment registers */