ACPI: EC: Evaluate orphan _REG under EC device

ACPI: EC: Evaluate orphan _REG under EC device

After starting to install the EC address space handler at the ACPI
namespace root, if there is an "orphan" _REG method in the EC device's
scope, it will not be evaluated any more.  This breaks EC operation
regions on some systems, like Asus gu605.

To address this, use a wrapper around an existing ACPICA function to
look for an "orphan" _REG method in the EC device scope and evaluate
it if present.

Fixes: 60fa6ae6e6d0 ("ACPI: EC: Install address space handler at the namespace root")
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218945
Reported-by: VitaliiT <vitaly.torshyn@gmail.com>
Tested-by: VitaliiT <vitaly.torshyn@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>