drm/i915/dsb: Pass DSB engine ID to intel_dsb_prepare()

Allow the caller of intel_dsb_prepare() to determine which DSB
engine (out of the three possible per pipe) to use. This will
let us utilize multiple DSB engines during the same commit.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240531114101.19994-4-ville.syrjala@linux.intel.com


Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>