HID: wacom: insert timestamp to packed Bluetooth (BT) events

stable inclusion
from stable-v5.10.180
commit 4502ebbdc0e21e44a8a706428e420ae9c1bb9bba
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I8FC2O

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4502ebbdc0e21e44a8a706428e420ae9c1bb9bba



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commit 17d793f3 upstream.

To fully utilize the BT polling/refresh rate, a few input events
are sent together to reduce event delay. This causes issue to the
timestamp generated by input_sync since all the events in the same
packet would pretty much have the same timestamp. This patch inserts
time interval to the events by averaging the total time used for
sending the packet.

This decision was mainly based on observing the actual time interval
between each BT polling. The interval doesn't seem to be constant,
due to the network and system environment. So, using solutions other
than averaging doesn't end up with valid timestamps.

Signed-off-by: Ping Cheng <ping.cheng@wacom.com>
Reviewed-by: Jason Gerecke <jason.gerecke@wacom.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: sanglipeng <sanglipeng1@jd.com>