ACPI / EC: Cleanup logging/debugging splitter support.

This patch refines logging/debugging splitter support so that when DEBUG is
disabled, splitters won't be visible in the kernel logs while they are
still available for developers when DEBUG is enabled.

This patch also refines the splitters to mark the following handling
process boundaries:
  +++++: boundary of driver starting/stopping
         boundary of IRQ storming
  =====: boundary of transaction advancement
  *****: boundary of EC command
         boundary of EC query
  #####: boundary of EC _Qxx evaluation

The following 2 log entries are originally logged using pr_info() in order
to be used as the boot/suspend/resume log entries for the EC device, this
patch also restores them to pr_info() logging level:
 ACPI : EC: EC started
 ACPI : EC: EC stopped

In this patch, one log entry around "Polling quirk" is converted into
ec_dbg_raw() which doesn't contain the boundary marker.

Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>