dts: xtensa: intel_adsp: Set soft-off state as disabled

Configure the 'soft-off' power state for manual selection only in the
DTS for Intel ADSP ACE 1.5 MTPM and ACE 2.0 LNL platforms.

Changes include:
- Setting 'min-residency-us' to 0 to indicate that the 'soft-off' state
  is not intended for automatic selection by the power management
  policy.
- Adding a 'status' property set to "disabled" to prevent the power
  management policy from using this state during its decision process.

The 'soft-off' state remains available for manual selection by calling
`pm_state_force`. This change ensures that the state can still be used
when explicitly requested by the system or application, providing
flexibility for power management operations.

Signed-off-by: Tomasz Leman <tomasz.m.leman@intel.com>