ACPI: Adjust #ifdef for *_lps0_dev use

The `#ifdef` for acpi_register_lps0_dev() currently is guarded against
`CONFIG_X86`, but actually the functions contained in the block are
specifically sleep related functions.
Adjust the guard to also check for `CONFIG_SUSPEND`.

Signed-off-by: Mario Limonciello <mario.limonciello@amd.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>