llvm-gcc checks the static asm variable is valid in ValidateRegisterVariable. Make this work for PPC.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@78051 91177308-0d34-0410-b5e6-96231b3b80d8

test/FrontendC/2004-03-16-AsmRegisterCrash.c

@@ -1,6 +1,10 @@
 // RUN: %llvmgcc -S %s -o - | llvm-as -f -o /dev/null
 
 int foo() {
+#ifdef __ppc__
+  register int X __asm__("r1");
+#else
   register int X __asm__("ebx");
+#endif
   return X;
 }