drm/i915/scaler: Compute scaling factors for pipe scaler

Compute scaling factors and scaler user for pipe scaler if
particular scaler user is pipe scaler.

--v2:
- Fix typos. [Ankit]
- Remove FIXME tag. [Ankit]
- Should be common hscale, vscale instead of local one to
avoid garbage overwritten.

--v3:
- Separate out max_scaling information. [Ankit]
- Use max_hscale and max_vscale info instead of INT_MAX. [Ankit]

--v4:
- Add Suggested changes reported by Dan Carpenter.

Signed-off-by: Mitul Golani <mitulkumar.ajitkumar.golani@intel.com>
Reviewed-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20250121175856.447245-1-mitulkumar.ajitkumar.golani@intel.com