ACPI: EC: Use proper handle for boot EC

Fall back to ACPI_ROOT_HANDLE only in case of error.

ACPI: EC: EC description table is found, configuring boot EC
ACPI Error (evregion-0316): No handler for Region [ECOR] (ffff81007a651620) [EmbeddedControl] [20070126]
ACPI Error (exfldio-0289): Region EmbeddedControl(3) has no handler [20070126]

http://bugzilla.kernel.org/show_bug.cgi?id=9916

Signed-off-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>