It's been discovered that BT controller disconnect events correlate to
erratic input report timestamp deltas.

In experimentation, it's been found that ensuring that multiple
timestamp deltas are consistent prior to transmitting a rumble packet
drastically reduces the occurence rate of BT disconnects.

Alter the joycon_enforce_subcmd_rate() function to use this new
approach.
Signed-off-by: Daniel J. Ogorchock <djogorchock@gmail.com>
Reviewed-by: Silvan Jegen <s.jegen@gmail.com
Signed-off-by: Jiri Kosina <jkosina@suse.cz>