ACPI: remove CONFIG_ACPI_EC

Remove CONFIG_ACPI_EC.  It was always set the same as CONFIG_ACPI,
and it had no menu label, so there was no way to set it to anything
other than "y".

Per section 6.5.4 of the ACPI 3.0b specification,

    OSPM must make Embedded Controller operation regions, accessed
    via the Embedded Controllers described in ECDT, available before
    executing any control method.

The ECDT table is optional, but if it is present, the above text
means that the EC it describes is a required part of the ACPI
subsystem, so CONFIG_ACPI_EC=n wouldn't make sense.

Signed-off-by: Bjorn Helgaas <bjorn.helgaas@hp.com>
Acked-by: Alexey Starikovskiy <astarikovskiy@suse.de>
Signed-off-by: Len Brown <len.brown@intel.com>