6827383 ddi_timer needs to be cleaned up

6617810 use of timer_taskq_min_num and timer_taskq_max_num might is incorrect.

6612330 ddi_timer.c seems heavy-handed on taskq threads
6612594 The variable clock_cyclic should not be updated after cyclic_timer is initialized.

PSARC 2007/402 Driver Periodic Timeouts
4977787 Official DDI interface is required for periodic timeout requests