Revert "timerfd: add alarm timers"

This reverts commit 4b4fab8e131fa092a1bb3a5c76f963eef88fbccb.
Revert "alarmtimer: add alarm_expires_remaining"

This reverts commit c7437928a6d7f067316a6a6056ade25e7102315c.
Revert "alarmtimer: add alarm_start_relative"

This reverts commit 2b6ca3e3afcaa510508308ebff210ac998aca08a.
Revert "alarmtimer: add alarm_forward_now"

This reverts commit 4b94c7242992da0941d11ff2c5f5544c7088d0e0.
Revert "alarmtimer: add alarm_restart"

This reverts commit 95632a0f4e5a7bf24b41f6197a0ee5399adba04d.