perf dwarf: Avoid redefinition warnings for REG_DWARFNUM_NAME

dwarf-regs.c includes an arch-specific dwarf-regs-table.h for several
architectures. This pulls in different definitions of REG_DWARFNUM_NAME
and causes compiler warnings for W=1 builds.

In file included from util/dwarf-regs.c:23:

  .../dwarf-regs-table.h:5: error: "REG_DWARFNUM_NAME" redefined [-Werror]
   #define REG_DWARFNUM_NAME(reg, idx) [idx] = reg

Undefine REG_DWARFNUM_NAME before each new definition.

Suggested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: Martin Kaiser <martin@kaiser.cx>
Cc: Ian Rogers <irogers@google.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/powerpc/include/dwarf-regs-table.h

@@ -7,6 +7,7 @@
  * http://refspecs.linuxfoundation.org/ELF/ppc64/PPC-elf64abi-1.9.html
  * http://refspecs.linux-foundation.org/elf/elfspec_ppc.pdf
  */
+#undef REG_DWARFNUM_NAME
 #define REG_DWARFNUM_NAME(reg, idx)	[idx] = "%" #reg
 
 static const char * const powerpc_regstr_tbl[] = {

tools/perf/arch/riscv/include/dwarf-regs-table.h

@@ -2,6 +2,7 @@
 #ifdef DEFINE_DWARF_REGSTR_TABLE
 /* This is included in perf/util/dwarf-regs.c */
 
+#undef REG_DWARFNUM_NAME
 #define REG_DWARFNUM_NAME(reg, idx)	[idx] = "%" #reg
 
 static const char * const riscv_regstr_tbl[] = {

tools/perf/arch/s390/include/dwarf-regs-table.h

@@ -2,6 +2,7 @@
 #ifndef S390_DWARF_REGS_TABLE_H
 #define S390_DWARF_REGS_TABLE_H
 
+#undef REG_DWARFNUM_NAME
 #define REG_DWARFNUM_NAME(reg, idx)	[idx] = "%" #reg
 
 /*