perf arm: Fix off-by-one directory path

perf arm: Fix off-by-one directory path

Relative path include works in the regular build due to -I paths but may
fail in other situations.

Fixes: 83869019c74cc2d0 ("perf arch: Support register names from all archs")
Reviewed-by: German Gomez <german.gomez@arm.com>
Signed-off-by: Ian Rogers <irogers@google.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexandre Truong <alexandre.truong@arm.com>
Cc: Athira Jajeev <atrajeev@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: James Clark <james.clark@arm.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220114064822.1806019-1-irogers@google.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>