drm/imx: error path fixes and cleanups

- Fix use after free issue in component bind error path by keeping
  memory allocated as long as the driver is bound. This will be replaced
  with drm managed memory in the next round.
- Fix bus_flags overriding logic in parallel-display.
- Disable regulator in imx-tve bind error path.
- Drop unnecessary best_encoder callback.
- Remove an unused enum in imx-ldb.
- Bail out early on missing panel or bridge in parallel-display to speed
  up -EPROBE_DEFER path.
- Disable both LDB channels in split mode.
- Restore RGB32, BGR32 format support.
- Fix tiled image conversion in case of out of order interrupts.
- Remove a superfluous error message in imx-tve.
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