[PowerPC] Reduce names from Power8Vector to P8Vector

Per Hal Finkel's review, improving typability of some variable names.

llvm-svn: 219514
diff --git a/llvm/lib/Target/PowerPC/PPC.td b/llvm/lib/Target/PowerPC/PPC.td
index f13be4a..46d56a4 100644
--- a/llvm/lib/Target/PowerPC/PPC.td
+++ b/llvm/lib/Target/PowerPC/PPC.td
@@ -104,10 +104,9 @@
 def FeatureVSX       : SubtargetFeature<"vsx","HasVSX", "true",
                                         "Enable VSX instructions",
                                         [FeatureAltivec]>;
-def FeaturePower8Vector : SubtargetFeature<"power8-vector", "HasPower8Vector",
-                                           "true",
-                                           "Enable Power8 vector instructions",
-                                           [FeatureVSX, FeatureAltivec]>;
+def FeatureP8Vector  : SubtargetFeature<"power8-vector", "HasP8Vector", "true",
+                                        "Enable POWER8 vector instructions",
+                                        [FeatureVSX, FeatureAltivec]>;
 
 def DeprecatedMFTB   : SubtargetFeature<"", "DeprecatedMFTB", "true",
                                         "Treat mftb as deprecated">;