Add ExynosAuto ABOX generic platform and PCM support

[ew kim]

This patch series adds the ABOX Generic audio management driver for
Samsung ExynosAuto SoCs, along with IPC messaging and PCM frontend
drivers, including their corresponding device tree bindings.

### ABOX Architecture Design: Fixed and Variable Structure

The ABOX audio framework is designed with a clear split between:
- **Fixed part** (common framework): reusable components across SoCs
  - Generic ABOX platform driver
  - IPC messaging handler
  - PCM frontend with ALSA compressed audio support
  - Solution manager for dynamic control
- **Variable part** (SoC-specific): defined via device tree
  - IRQ numbers, stream IDs, buffer sizes, and ADSP allocation
  - Defined per PCM/IPC device node in DTS

This separation allows the fixed part to be upstreamed and maintained
as a reusable framework, while only the DTS and minimal changes are
needed to adapt to each SoC generation.

### Major Components in This Series

- `abox_generic`: Root platform driver coordinating subcomponents
- `abox_ipc_generic`: Handles ADSP messaging via IRQ-based IPC
- `abox_pcm_dev`: PCM frontend with support for solution chain selection
- `abox_solution_mgr`: Manages software-based audio chains via dynamic
  kcontrols

### Testing

Tested on ExynosAuto v920 board:
- Verified ALSA compressed audio playback via DSP
- Confirmed solution switching via kcontrol
- Verified DT node parsing and IRQ routing from device tree