[PATCH, libgcc] Fixup _UnwindGetGR for function argument rename

[Uros Bizjak]

Revision 256615 (SVE unwinding) renamed _UnwindGetGR function
argument, but forgot to update part under #ifdef DWARF_ZERO_REG.

2019-02-19  Uroš Bizjak  <ubiz...@gmail.com>

    * unwind-dw2.c (_Unwind_GetGR) [DWARF_ZERO_REG]: Compare
    regno instead of index to DWARF_ZERO_REG.

Bootstrapped on alphaev68-linux-gnu and committed to mainline and
gcc-8 as obvious.

Uros.

diff --git a/libgcc/unwind-dw2.c b/libgcc/unwind-dw2.c
index bd88df963957..e6130af2fb54 100644
--- a/libgcc/unwind-dw2.c
+++ b/libgcc/unwind-dw2.c
@@ -225,7 +225,7 @@ _Unwind_GetGR (struct _Unwind_Context *context, int regno)
   _Unwind_Context_Reg_Val val;
 
 #ifdef DWARF_ZERO_REG
-  if (index == DWARF_ZERO_REG)
+  if (regno == DWARF_ZERO_REG)
     return 0;
 #endif