migration: HMP: Fix possible out-of-bounds access

migration: HMP: Fix possible out-of-bounds access

Coverity has caught a bug in the formatting of time intervals for
postcopy latency distribution display in 'info migrate'.

While bounds checking the labels array, sizeof is incorrectly being
used. ARRAY_SIZE is the correct form of obtaining the size of an
array.

Fixes: 3345fb3b6d ("migration/postcopy: Add latency distribution report for blocktime")
Resolves: Coverity CID 1612248
Suggested-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Link: https://lore.kernel.org/qemu-devel/20250716182648.30202-2-farosas@suse.de
Signed-off-by: Fabiano Rosas <farosas@suse.de>