ACPI: EC: PM: Make acpi_ec_dispatch_gpe() print debug message

Add a pm_pr_dbg() debug statement to acpi_ec_dispatch_gpe() to print
a message when the EC GPE has been dispatched (because its status
was set).

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Kai-Heng Feng <kai.heng.feng@canonical.com>