perf tools: Fix build breakage on arm64 targets

Attempting to build the perf tool for an arm64 target results in the
following failure:

  arch/arm64/util/unwind-libunwind.c: In function 'libunwind__arch_reg_id':
  arch/arm64/util/unwind-libunwind.c:77:3: error: implicit declaration of function 'pr_err'
     pr_err("unwind: invalid reg id %d\n", regnum);
     ^
  arch/arm64/util/unwind-libunwind.c:77:3: error: nested extern declaration of 'pr_err'

This is due to commit 84f5d36f48 ("perf tools: Move pr_* debug macros
into debug object") moving the pr_* macros into a new header file, but
failing to update architectures other than x86.

This patch adds the missing include, and fixes the build again.

Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: linux-arm-kernel@lists.infradead.org
Link: http://lkml.kernel.org/r/1412076432-22045-1-git-send-email-will.deacon@arm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/arch/arm64/util/unwind-libunwind.c

@@ -3,6 +3,7 @@
 #include <libunwind.h>
 #include "perf_regs.h"
 #include "../../util/unwind.h"
+#include "../../util/debug.h"
 
 int libunwind__arch_reg_id(int regnum)
 {