hms: Workaround idle mouse drift in I2C sampling mode.

Many I2C "compatibility" mouse devices found on touchpads continue to
return last report data in sampling mode after touch has been ended.
That results in cursor drift. Filter out such a reports with comparing
content of current report with content of previous one.

Reported by: many
Tested by: omatsuda, gllb (github.com)
Obtained from: sysutils/iichid