ACPI: DPTF: Use ACPI_FREE() for ACPI buffer deallocation

ACPI: DPTF: Use ACPI_FREE() for ACPI buffer deallocation

Replace kfree() with ACPI_FREE() in pch_fivr_read() to follow ACPICA
memory management conventions.

While functionally equivalent in Linux (ACPI_FREE() is implemented
as kfree()), using ACPI_FREE() maintains consistency with ACPICA
coding standards for deallocating ACPI buffer objects.

Signed-off-by: Kaushlendra Kumar <kaushlendra.kumar@intel.com>
[ rjw: Subject and changelog edits ]
Link: https://patch.msgid.link/20251028051554.2862049-1-kaushlendra.kumar@intel.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>