ACPI: x86: s2idle: Post-increment variables when getting constraints

When code uses a pre-increment it makes the reader question "why".
In the constraint fetching code there is no reason for the variables
to be pre-incremented so adjust to post-increment.
No intended functional changes.

Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Suggested-by: Bjorn Helgaas <helgaas@kernel.org>
Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>