perf arm-spe: Fix a dangling Documentation/arm64 reference

The arm64 documentation has moved under Documentation/arch/. Fix up a
dangling reference to match.

Cc: Peter Zijlstra <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Acked-by: Catalin Marinas <[e-mail]>
Acked-by: Arnaldo Carvalho de Melo <[e-mail]>
Signed-off-by: Jonathan Corbet <[e-mail]>

tools/perf/util/arm-spe-decoder/arm-spe-decoder.c

···
 		 * (bits [63:56]) is assigned as top-byte tag; so we only can
 		 * retrieve address value from bits [55:0].
 		 *
-		 * According to Documentation/arm64/memory.rst, if detects the
+		 * According to Documentation/arch/arm64/memory.rst, if detects the
 		 * specific pattern in bits [55:52] of payload which falls in
 		 * the kernel space, should fixup the top byte and this allows
 		 * perf tool to parse DSO symbol for data address correctly.