block: avoid setting nr_requests to current value

block: avoid setting nr_requests to current value

BugLink: https://bugs.launchpad.net/bugs/1815733
There's no reason to freeze queue and set nr_requests value
if current value is the same.

Signed-off-by: Aleksei Zakharov <zakharov.a.g@yandex.ru>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
(backported from commit e5fa81408fb43ebabde65938ef8b20ae879017e7)
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Acked-by: Kleber Souza <kleber.souza@canonical.com>
Acked-by: AceLan Kao <acelan.kao@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>