[Driver] Pass +reserve-x25 to backend if -ffixed-x25 is specified

This was accidentally omitted in r353957 breaking the Clang test.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@353960 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Driver/ToolChains/Arch/AArch64.cpp

@@ -373,6 +373,9 @@ fp16_fml_fallthrough:
   if (Args.hasArg(options::OPT_ffixed_x24))
     Features.push_back("+reserve-x24");
 
+  if (Args.hasArg(options::OPT_ffixed_x25))
+    Features.push_back("+reserve-x25");
+
   if (Args.hasArg(options::OPT_ffixed_x26))
     Features.push_back("+reserve-x26");