ACPI: EC: Clean up probing for early EC

Both acpi_ec_dsdt_probe() and acpi_ec_ecdt_probe() may be void as
their return values are ignored anyway.  This allows a couple of
gotos and labels to go away from there.

Moreover, acpi_ec_ecdt_probe() only needs to allocate the ec
object after getting the ECDT pointer and checking it, so the
pointless memory allocation and release on systems without the
ECDT can be avoided by reordering it.

No intentional functional impact.

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