ACPICA: Fix memory leak if acpi_ps_get_next_field() fails

ACPICA commit 1280045754264841b119a5ede96cd005bc09b5a7

If acpi_ps_get_next_field() fails, the previously created field list
needs to be properly disposed before returning the status code.

Link: https://github.com/acpica/acpica/commit/12800457


Signed-off-by: Armin Wolf <W_Armin@gmx.de>
[ rjw: Rename local variable to avoid compiler confusion ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>